i would recomend getting 5 new nuts and a 2 spare studs for where the down pipe bolts on to the turbo flange before you attempt to change the down pipe. you may not need them, but if they've not been moved in a while, the nuts can be a complete ars3 to get off and are easily rounded.
better to spend an extra £15 and be able to complete the job rather than find out too late that you've gotta order them before you can use tha car again!
give
these guys a call if you can't get hold of the nuts/studs elsewhere.