It's not too difficult at all jason.
Swapped mine recently for MOT time. A couple of points to think about though....
Getting the holes to line up was a bit of a puzzle - succeeded after a lot of tugging on the pipes. I'm assuming that where the original pipes were sitting in the attick for ages that the temp changes had slightly mis-shaped them, but it wasn't too much trouble.
Another thing I found out was that the silencer clamps from the Termi's don't fit the standard cans so not having the original clamps, I had to fashion some out of some old ally plate I had lying about. This was a total bodgit job so I'd recommend you get some original clamps if you've not already got some.
And finally...... watch out for them springs - they bite!
Threaded Mode