Roger, here are a couple links that may help. They are not for a Ricoh, but the concept, and placement of the seals, should be the same. It is on my Sears KS-2 (Ricoh XR-7).
It's important to mask off the area near the shutter so as to not get any debris in there.
I used toothpicks (wooden and plastic) to scrape out the old foam, and a bit of solvent on Q-tips to clean things a bit. I did not use a kit, or even foam, though may revisit my repair in the future.
For the channel (groove) in the body I used wool yarn. I cut a thick piece of felt for the area where the rear door is attached to the hinge. If you see no foam there, you're likely to see residue in the spot it used to be.
The less-brilliant thing I did was to use rubber cement to hold the yarn and felt in place. I applied it in the channel with a toothpick. Many kits have self-adhesive foam, so that should not be an issue. The reason I used rubber cement is that it can be removed easily if I did something wrong or decided to re-do it. I cleaned up the mirror-box area, but did not replace anything there yet.
So far I've had no problems.