I am not - by any chance - telling you what to do; only bringing food for thoughts and trying to introduce a different perspective for your consideration.
If indeed there is no rot on the transom - very slim chance - but let's assume for the sake of argument that there is no rot; you will still need to get inside and demolish the wood to get to the fiberglass skin, grind it and rebuild it. So this is replacing the transom just as a by product. You can do the repair from the outside but your desire to restore this boat to original status makes fixing from outside not practical or very expensive to restore the cosmetic look of the boat (i.e. most likely you will need to gel or paint the entire hull to hide the repair area.
If you decide fix from the inside, this will involve the following
- Separting the cap, wires and everything that connect to two halves of the hull
- Remove the engine
- Remove the transom
Of course, of course you will not be that far in the boat and will ignore that little rot that started in the stringers (believe me, 95% chance it is there)
What about this black spot on the bulkhead?!... Post pictures... iBoaters, what you think I should do?!
SloppyJoe : Ignore it and go boating
The rest of us : you can't be that close and ignore this... do it right... do it once and be done with it.
Before you know it you will be restoring the entire boat. Factor in outdated electronics, mechanical work (we don't know anything about the power train condition yet) and it can add up really really fast.
Assuming you love this boat and get it cheap enough to justify the restoration cost; few things to consider
This is a speed daemon, what is the gallons per mile (yes, it is the other way around not miles per gallon like a car) for this boat?
Is it suitable for your current or future social status; in other words are you married or planning to? Is this Mrs OK with a boat with no space move or go to the bathroom? Do you have kids?
Again, these are just things to consider when you are making your decision and maybe non of it might have any relevancy or importance to your situation. I only want to make sure you are covering all angles before you decide.
Now, there is a web site out there to review marine survivors and they have to be members of some association or such, I forgot the details. Just google how to evaluate or review a marine survivor and I am sure you will get the 411. See which one of the two has better experience/reputation and hire him for full survey. It will be the best $350 or $17/foot you ever spent.