When Michael fitted my dump pipe it didn't need any new gaskets and when you buy either a turbo-back or cat-back it should come with new gaskets.
I guess that doesn't mean that you won't need a new turbo/dump gasket though. If it's cheap to buy one maybe just get one anyway.
To fit the dump you will need to take off engine cover and TMIC and to do everything else a hoist would be beneficial...but you could do it with the car on ramps.
All the tools you'll need is a socket and spanner set
Edit: depending on the style of the dump pipe and where the cat is positioned you may need to trim the heat sheild, so some tin snips will come in handy