Hi, a 2.5 should be the same as a 2.0, it is the 3.0 that goes in the boot.
The swap is pretty straight forward, you need the tank, change the pipes underneath that go to the fuel pump (that stays the same) also the pipes and vents and finally the fillet beck and fuel cap need to be swapped. For a neat job, also get the boot carpet for a 3.0 as that covers the tank up nicely so it is not visible in the boot. You will also have to extend the wires for the fuel gauge as they are in the top of the new tank rather than at the front. And you will have to cut some holes in the boot floor for the piped to go through and a couple of slits for the tank straps to fit into, easy enough though.
Beware when buying your 3.0 tank, there is an area by the pipes at the bottom that rust just as bad as a 2.0 tank.
I think that is it.