You dont NEED a girdle. Its not gunna be the one and only reason the motor pops, but its never a bad idea.
Wont need a new ECU all togather, but your gunna need a tune for sure.
You can port and polish all you want, but the fact is, outa the box the VTEC heads already make good power as far as you wanna take the LS bottom end. Id save the money from P'n'P and put it towards things that are gunna ensure the LS bottom will hold togather. Like ARP fastners, fresh bearings, etc.
Like they said already though, if wiring VTEC is somethin you dont wanna do, then waste your time and money tryin to piece togather an LS/V setup.