^^^I'd avoid the above named company, but it IS better to go to one of the "tyre and exhaust" specialists rather than a normal "servicing" outfit...they'll do the job quicker (often while you wait) and cheaper.
Thanks for the replies. I've had a look online, and a back box for my make and model (a Saab) seems about £60. From what I can see, it's only a matter of unclipping the old one and connecting the new one. I hope so!
Yes, it is only a matter of unclipping the old one etc BUT - it will be rusted on, you'll be laid on your back with no room to move and wriggle to get the parts apart, then when you put the new one on it will leak. I gave up changing my own exhausts years ago when I found it cost hardly anything to have it fitted over doing it myself. Get a quote for a new box as a spare part, then check with specialist exhaust fitters and see if you still think it's worth the difference.
I completely agree with bhg...the job will take the professionals at an exhaust centre no time at all. Trying to do it yourself without proper access to the underside is not a job I'd now contemplate...it really doesn't cost much to have it done...and saves lots of time, bloody knuckles, pulled muscles etc!
As bhg say's ... don't get involved. Once you start a job like replacing a backbox at home you will more than likely find it is rusted onto the long pipe that goes forward to the engine. The clamps may also be rusted.
If you don't have an air chisel and goggles, make sure you have a supply of hacksaw blades before you start sawing above your head. You will also need loads of bad language, some clean cloths as well as bandages for the blood ..... and then you will end up taking your car to the exhaust fitters.
Don't worry, have no intention of trying to do the job myself! I've left it at the garage where it failed the MoT, but they still haven't contacted me. Why do garages NEVER ring to let you know what's happening?!