Agree with Adi. You'd want to change the entire body harness. Check out Uber Soldat's thread regarding his wagon, as he did just that. You could chat to him for some advice I guess.
From what I have researched, taking the carpet out requires removing both centre consoles, plastic sill covers (they clip into the body through the carpet), B-pillar covers, footwell speaker covers and you'd have to take out the seatbelt height adjusters as well. The last tricky part would be pulling out the front carpet from under the heater core. Getting it out is easy, getting it back in is difficult. Most people cut the carpet either side of the heater core to get it out.
You have three separate harnesses. Body, engine bay and dashboard. They plug into each other under the glovebox. It seems though, to get the entire body harness out, the doors would have to come off. The harness also runs into the boot area and up into the trunk lid. The harness that goes to the sunroof unplugs as far as I know. Quite a task, but doable.
Again...it may be an idea to chat to Uber Soldat.