I think replacing carpet is an easy project. It could be done in an afternoon by one person. I might suggest doing it on a warm day and perhaps laying the carpet in the sun for a very short time. Makes it a little more flexible. I did very little trimming,most of it up front near the kick panels. On my carpet, I did have to cut for the seat and console mounts as well as the shifter cable. No big deal.
Interior work is not bad....The carpet is much easier than say... doing the vinyl for seats, which can be challenging. The head liner, I would say is the most difficult to get good results. I left that to a pro. Door panels too are quite easy. Removing the dash is a can of worms.
Some of the fastners are quite hard to get to and you need to be a contortionist. This is where the factory service manual is a must.
Good luck, you've come a long way and youre allmost there.