Depends if you are doing this to your Red Top Cav (the GSI) If you are removing the centre section on this car, it's very easy aslong as you have purchased a replacement part made for your car.
All you need to do is jack up one side of the car and get a 13mm ratchet then there is 3 bolts on each flange, undo them and the centre section should just drop out.
If you have an exhaust that has been connected just by sliding one section into another but with exhaust clamps, then just undo the back box end first (closest to the rear) then push the back box towards the back of the car and it will just slide off, then do the same with the other join and bobs ya uncle
Again, if you are doing this to your GSi, I would higly recommend you get the power cap from Courtenay for the inlet, the custom inlet manifold, uprated downpipe and a sports cat, then get it mapped, should see you a nice healthy 15-20bhp
Then you can think about cams etc