Lots of things "could have happened", but you have to start somewhere to figure it out.

First thing I would do is find out "if it has any oil pressure". Pull the oil sender and install a test oil gauge. Pull the distributor out and make up an oil pump drive rod. Take a 1/4" drive deep socket and weld a drill rod (or old screw driver shaft) to it so you can run the oil pump with an electrict drill for the test.

It this checks OK, put the distributor back in and repeat the test with the engine running. You might have stuck open the pressure relief valve.

As far as the valve stem seals, it's easy to replace them with the heads and manifold still on, in the car. All you need is an old rocker shaft, the K&D spring tool and just put the cylinder on TDC, one at a time. If your worried, you can use the compressed air method.

If you lost oil pressure, one of the first audiable signs will be rattling hydralic lifters.