Not much - kick panel, the trim around the seat base, the sill plate, side of centre console, and the panel above the footwell. A few bits, but none are really difficult. Then you should be able to lift the carpet and manhandle it enough to get a stanley knife under to cut the foam.
On my original 96, the foam was bonded to the thick rubber / plastic type material, so I cut through that and removed it together. On my current one, the thick rubber/plastic bit seems to be bonded to the carpet and the foam is separate, so I just cut the foam out. In either case the carpet does not get cut and just folds back down to hide the missing underlay for the time being. When its dried out, it will sit in place quite nicely despite being cut.
Southampton with a Nanocom for Thor/GEMS P38s
1996 4.6 HSE, then became a 4.0, now cubed.
1997-8 4.6 HSE Motronic/Wabco prototype vehicle. Now M57 powered. Still auto.