Yeah the gearbox cross-member is a bit sus. If your admit its strong enough you should be alright.
Otherwise you might have to swap it over.
Coilovers could cause you grief as they are illegal. If your lucky they can overlook that as they're are only "engineering" the brakes.
Just make sure it all looks neat and tidy and the car as a whole. They will more likely let coilovers go if they don't think your gunna be getting pulled over and going thourgh qt inspections.
Doubt they would want documentation on such a simple conversion.
Can't really help on price but I would say if its cost over $500 its too much.
The guy I use doesn't like doing it because of the paper work. haha.
I've know of two people that went through http://modplate.com.au/ and said it was good. It was more minor stuff though.