There is something wonderful about tearing an engine down and rebuilding it. There are varied complexities but all are great. Well, except for the engine in the old Colt Vista. That was not fun.
If you get the chance, go ahead and do it. There are many resources to guide you, unless it's a very rare engine. Even then, the principles are the same.
It's a lot of fun and fascinating to see how they work.
... but remember to get new gaskets. The older they are, the chances get higher that they'll break on dismantling and you don't want to rebuild the engine and have it go boom the first time you turn it on ;)
If a rebuild didnt include setting timing and gaskets I would be very worried. It usually implies precision machining on the head, block, and valves, new pumps, rings, etc.
Ah sorry, I mixed up the words... I meant "reassembling". It definitely helps with old cars to tear them down, clean (and repaint!) everything, replace all worn-down parts and then put it together again, without going as deep as re-boring cylinder holes and inserting new pistons - that one definitely requires a skilled expert as well as specialized tools, while all you need for a disassemble-cleanup-reassemble can be done at a hobby garage or in your shed if you have a sufficiently large shed and a well sorted toolbox.
If you get the chance, go ahead and do it. There are many resources to guide you, unless it's a very rare engine. Even then, the principles are the same.
It's a lot of fun and fascinating to see how they work.