To answer the second part of your question: It would be a good idea to stiffen the transom of your boat by using a couple layers of marine plywood as a backer board and epoxying that to the inside face of the transom. It takes a litle flexibility to crawl inside the hull, but it is doable. Once this is done, you can throughbolt a mounting on the transom side (any good beefy motor mount will do, but I recommend not skimping on money for it. I would get one with a hydraulic assist to tilt the motor up out of the water when not in use. It's a very awkward angle and bad for your back to get one that you have to tilt out without the hydraulics. I set the motor mount on a piece of plastic cutting board bought at West Marine and cut down to the proper size for the mount. The mount and backer were then through bolted through the transom and marine ply, and all the bolts were coated with 3M epoxy sealant. My only complaint about the transom mount is that it's inelegant, the motor cavitates in swells, as the motor is aft of the rudder you need a little headway to steer properly at first which can make for interesting docking in heavier wind, and it probably effects the dynamics of the boat a little under sail as the engine is heavy and therefore slightly unbalances the boat. Otherwise the only solution is to find a small diesel and mount it amidship with a through hull drive. I looked into this (as I had an original gas engine with a Baldwin through hull drive) but it costs upwards of $7000 to do this. More than the boat is worth. Good luck.
FYI: I was thinking of the very same tiller to wheel conversion for my C-26 (hull#860). I contacted Edson. They sent me a catalog with a letter appologizing for not having the plans for my particular boat. I understand trying to clear the pit. Would be nice. Please feel free to message me if you find a suitable way of doing it.