Oil leak

It's pretty common to have a small engine oil leak at the rear main seal where the crankshaft meets the engine block. But if it's transmission fluid, then the torque convertor has seepage if this is an automatic. Either way it's not serious. On my older, high mileage vehicles I use that STP engine additive that softens and smells the seals. That stuff really works! They might have the same for transmissions.

The leak mentioned is on a 2015 F250 6.2L V8 with 57,000 miles. It is definitely oil and not transmission fluid.

Is it critical that a leak like this is repaired immediately? What are the risk being that it was a dime size drop or less 2 times on my driveway over a 8 day period. I drive the truck 25 miles round trip to work and back and have only seen this drop twice.

Repairing a tiny leak like this is totally unnecessary. It will not suddenly fail and drain the engine of it's oil. I doubt it would get much worse. And a repair would entail replacing the entire engine costing thousands of dollars when motor oil is only $3 a quart. That truck is almost new and your concern shows that you probably take great care of it. Just keep up the maintenance and enjoy your truck.

I'm not following on repairing the leak and how it would entail replacing the entire engine.

If it's a leak at the rear main seal, the entire engine would have to be removed from the truck and totally disassembled right down to removing the crankshaft to replace the seal. This is commonly referred to as a Mechanic's Nightmare. It would be so labor intensive, the easier option would be to drop in a new engine so you have a truck to drive before your next birthday. I know, I've done them.

You do NOT have to remove the engine in order to replace the rear main seal on a 6.2 You can drop the transmission and have adequate room. The rear main has its own housing that is easily removed from the back of the engine.