it's probably your piston rings. you may get away with having your pistons/rings replaced, but if your cylinder walls are damaged, you may need to get it bored and put slightly bigger pistons in.
Crank seals should have nothing to do with your compression. If you have bad compression it is your top end. Pistons, rings, cylinders. That is where I would start. Sometimes if the engine has been sitting for a long time you may need to get some oil in your cylinder walls to get the rings to seal up again. You should hope it is top end because as expensive as that is to fix it is cheaper than crank seals and bearings...rebuilt crank.