It's not too difficult to do yourself. Get some large pieces of card to use as templates for where the wheel boxes meet the front bulkhead. Don't stick down the floor piece, as that way you can take it out and replace it when it gets worn out, plus it helps when keeping the back clean.
The carpet in the back of my 90 also up the inside of the side panels slightly- just to the top of the curved part. I suggest covering the rear side of the bulkhead as well while you're doing the floor- it should help protect it against stuff banging around in the back.