I would not jump to conclusions about bad bearings. There other more likely culprits to cause a no-start-when-warmed-up situation.
Overheating.
Dirty spark plugs.
Dirty battery terminal connections.
Weak starter.
Ignition timing off.
Coil going bad.
Carburetor out of adjustment or worn out.
Before you ever start this engine, make certain that you do not use the current gas tank as the fuel supply. There will be crud and varnish in it which will cause you some major headaches, if not nearly catastrophic engine damage. I small boat engine tank is very handy for supplying gas to the engine for testing. The priming bulb comes in handy too.
I would recommend checking all of these items in the order listed before ever dropping the oil pan to check the bearings.
