Head gaskets on M103s are almost as wide spread as M104s. I'd say its a coin flip if you'll ever have to deal with it in the next decade. I've owned 1 M103 and 2 M104s, none of which were on their original head gaskets.
I hope your AC works. If you don't have much oil consumption between oil changes don't worry about the valve seals.
Iwrock has gotten 253k out of 4 engines.
Please post photos of the 3.6 swap.
