It's my opinion some people should not got down this path, they're simple not suited to the problems you invariably come across.
Makes no difference if you're swapping a 25 in place of 20 or going for a V8, you will have some dramas along the way.
With all the info available on the net these days, one would expect a straight Rb to Rb swap to be easy but that hasn't been my experience, you need patience and some clear headed pin out ability when it comes to the wiring.
Forget an auto sparky unless you have very deep pockets. Usually you're simply paying him to learn.
You also need to sift through the mass of mis-information given on the net, a LOT is simply rubbish.
Talk to the guys who have actually done the full hands-on swap, not the keyboard heroes.