Don't know where you are at, but if you have the local machine shop do the machining, you're in for a rude awakening...most have a $150.00 to $300.00 min. charge...or $60.00 an hour charge if they like you, but it ya have a friend with a small lathe in is basement or garage ya come out way ahead...
People on here that are doing a lot of conversions may already have the parts made that you need, no fuss no muss..

The common conversion is cut the fins down to the front of the fly wheel, machine up a prop adapter that fits over the crank and against the now machined fly wheel and a spinner nut and washer...
It's not really that hard, so don't let it scare you...

Balance can be done static..taking small amounts off the heavy side with a drill, or a Dremil Tool..just don't take it all from one place and get thin spot..