Spell: Making one hero into another?

I would like to make this spell in neutral unit (like a shop) and somehow when my hero gets close, lets me use the spell.

The spell that I would like is making one hero into another with level requirements.
So basically, If "HERO" becomes level 10, I would be able to click on that skill and change to another hero with the same level that I was.

I have no idea what spell I would have to base it on. I know I would probably use triggers too.

Can you please help me?

I am doing that too! ^^
Well u can use morph as base hability or use "any" hability just as a dummy n do it all in gui, customtext(my case) or jass.

Ill guide u to the source: http://www.world-editor-tutorials.th....net/index.php

ok its not anymore there....but there r nice tutorials....

The map is here at the bottom: http://www.wc3campaigns.com/showthread.php?t=74915 look for my avatar n download: Ryoko,Heroes,creeps n Items.w3x

you should probably make likea dummy ability that the hero learns by a trigger when it comes within a distance of the shop. and just change unit type when they use the ability...