Norm has some very sound comments, as usual. A restoration like this is an exciting prospect if you are of an age and wherewithall to deal with the time, cost and logistics.
If you are at the point in your life where you are willing to roll the dice and take a chance, then a project like this may be just what the doctor ordered.
For instance, about 15 years ago, I had a wood 35' Chris Craft Sea Skiff that I loved, but I knew at the time I was going to sell it because the maintenance on the hull was consuming more time than I wanted to be lying on my back scraping paint and fastening screws. Janet and I found our 38' Commander in Cincinnatti on the Ohio River, and at the time, I didn't get a mechanical review or did I care at the time. I was prepared to buy the boat and repower it if I had to, rather than wring my hands wondering about the mechanicals. As fate would have it, the motors did run and they continue to run well. Had they not run I would have found a way to either make them run or repower, and I am sure I would still have had at least 14 years of running time.
Most people are more careful but at the time I wanted a Commander and fully intended on buying the one that was available at the time. Perhaps not the smartest thing, but like I said, if you are of an age, wherewithall and can handle the logistics, this makes a difference in whetheer or not you should take on a project. They always cost more than you budget.
If you are limited to cosmetics and the yard will stand behind the mechanicals, that's good. However, one wonders how far they'll go if there are problems, they'll probably tell you they will assure the motors will run, and then it's up to you. Still, there are risks in life and everyone with an old boat takes them in kind.
I won't ask what the price is, but I paid too much for all of my boats, $25,000 for our 38 Express, and it needed a lot of careful interior work and mechanical ancillary attention.
On the interior, check out our refinishing section, there is a chance you do not have to destroy the interior, as it may look crappy now but could be restored nicely. There are numerous examples of this being done.
Here is the interior refinishing link
My interior, shown above, was varnished and very poorly at that. I was able to sand down the outer layer of varnish with a flat wood block, and do a little touch up, with many coats of interior wipe on poly furniture finish, and you can see the results here.
I know you said you had a Sedan in mind, but look at my Express below and you can see what a few new pieces of carefully selected mahogany plywood will do at the helm, those side pieces are new, and the frontal pieces around the helm are original, all carefully stained the same.
This sort of work takes a lot more time than it does cash.
There are several Commander projects showcased here in the MASTER INDEX restoration section that show boats taken all the way down to the fiberglass on the interior and exterior. It sounds like yours is ahead of the curve, but it may be for someone else. Therefore be sure to look further at the examples here, assess whether or not you have the time and cash, and whether or not you want to be spending time at the marina doing this sort of thing. It's in my blood, so I enjoyed just about every minute of it, but I can not recommend it to a friend or a stranger without due cautions and reality checking.
Good luck, keep us posted.