Sounds like you cant go wrong with installers mentioned above--Thought I would share with you-amoung other things I just had the corsa track exhaust that was spot welded and 3.55 gears installed. I will be picking up the car maybe tomorow evening from Ab.
The 3.55 gear ,at a dealer about 85 miles away, list as a 10 hr job. The dealer charged 85$ a hr. Theirs a lot of labor installing the gears. It takes quite a bit of time and know how to set it up right.
From the way Adam describes how my Viper is running, you are going to be thrilled with the corsa and gears. Cant wait to try it out myself.
Good luck steponz - I am sure you will like the two mods.
Keep us posted