Which NPC system do I need?

[ziggy46802]

Which npc system do I need for an npc like this:

?xml version="1.0"?>

<npc name="Billy"  script="default.lua" floorchange="0" walkinterval="4000" walkradius="10">
	<health now="150" max="150"/>
	<look type="133" head="10" body="122" legs="19" feet="10"/>

<interaction>

  <interact keywords="bank">
    <response text="The depots are very easy to use. Just step in front of them and you will find your items in them. They are free for all tibian citizens."/>
  </interact>

  <interact keywords="offer">
    <!--These are alternative keywords-->
    <keywords>sell</keywords>
    <keywords>money</keywords>
    <keywords>change</keywords>
    <keywords>buy</keywords>
    <keywords>exchange</keywords>
    
    <response text="We exchange gold, platinum and crystal coins."/>
  </interact>

  <interact keywords="change;gold">
    <response text="How many platinum coins do you want to get?">

      <interact keywords="|AMOUNT|">
        <response text="So I should change |N1| of your gold coins to |AMOUNT| platinum coins for you?">
          <action name="script" value="_state.n1 = _state.amount*100"/>

          <interact keywords="yes">
            <response>
              <action name="script">
              <![CDATA[
                if(getPlayerItemCount(cid, 2148) >= _state.amount*100) then
                  selfSay("Here you are.", cid)
                  doPlayerRemoveItem(cid, 2148, _state.amount*100)
                  doPlayerAddItem(cid, 2152, _state.amount)
                else
                  selfSay("Sorry, you don't have enough gold coins.", cid)
                end
              ]]>
              </action>
            </response>
          </interact>

          <interact keywords="|*|">
            <response text="Well, can I help you with something else?"/>
          </interact>
          
        </response>
      </interact>
      
    </response>
  </interact>

  <interact keywords="change;platinum">
    <response text="Do you want to change your platinum coins to gold or crystal?">
      
      <interact keywords="gold">
        <response text="How many platinum coins do you want to change to gold?">
          
          <interact keywords="|AMOUNT|">
            <response text="So I should change |AMOUNT| of your platinum coins to |N1| gold coins for you?">
              <action name="script" value="_state.n1 = _state.amount*100"/>

              <interact keywords="yes">
                <response>
                  <action name="script">
                  <![CDATA[
                    if(getPlayerItemCount(cid, 2152) >= _state.amount) then
                      selfSay("Here you are.", cid)
                      doPlayerRemoveItem(cid, 2152, _state.amount)
                      doPlayerAddItem(cid, 2148, _state.amount * 100)
                    else
                      selfSay("Sorry, you don't have enough platinum coins", cid)
                    end
                  ]]>
                  </action>
                </response>
              </interact>

              <interact keywords="|*|">
                <response text="Well, can I help you with something else?"/>
              </interact>

            </response>
          </interact>

        </response>
      </interact>
      
      <interact keywords="crystal">

        <response text="How many crystal coins do you want to get?">

          <interact keywords="|AMOUNT|">
            <response text="So I should change |N1| of your platinum coins to |AMOUNT| crystal coins for you?">
              <action name="script" value="_state.n1 = _state.amount*100"/>

              <interact keywords="yes">
                <response>
                  <action name="script">
                  <![CDATA[
                    if(getPlayerItemCount(cid, 2152) >= _state.amount*100) then
                      selfSay("Here you are.", cid)
                      doPlayerRemoveItem(cid, 2152, _state.amount*100)
                      doPlayerAddItem(cid, 2160, _state.amount)
                    else
                      selfSay("Sorry, you don't have enough platinum coins.", cid)
                    end
                  ]]>
                  </action>
                </response>
              </interact>

              <interact keywords="|*|">
                <response text="Well, can I help you with something else?"/>
              </interact>

            </response>
          </interact>

        </response>

      </interact>

    </response>
  </interact>


  <interact keywords="change;crystal">
    <response text="How many crystal coins do you want to change to platinum?">

      <interact keywords="|AMOUNT|">
        <response text="So I should change |AMOUNT| of your crystal coins to |N1| platinum coins for you?">
          <action name="script" value="_state.n1 = _state.amount*100"/>

          <interact keywords="yes">
            <response>
              <action name="script">
              <![CDATA[
                if(getPlayerItemCount(cid, 2160) >= _state.amount) then
                  selfSay("Here you are.", cid)
                  doPlayerRemoveItem(cid, 2160, _state.amount)
                  doPlayerAddItem(cid, 2152, _state.amount*100)
                else
                  selfSay("Sorry, you don't have enough crystal coins.", cid)
                end
              ]]>
              </action>
              </response>
          </interact>

          <interact keywords="|*|">
            <response text="Well, can I help you with something else?"/>
          </interact>

        </response>
      </interact>

    </response>
  </interact>
    
</interaction>

</npc>

to work? I don't want the newest most complicated system, I just want one that is stable and works with this basic type of stuff. By the way I am using OTServ 8.60 r.6052

I just want to be able to make everything work in the xml file (like selling/buying stuff, doing this example, and setting storage values for quest) and have all my npcs use a "default.lua" script file.