What makes you think the motor is on it's way out apart from it not feeling as quick? That's a very vague description. Mine was missing a piece of the piston crown and it still pulled like crazy so I wouldn't base your assumption off that alone.

Oil consumption is pretty much the best indicator regarding damaged pistons without digging deeper. Mine was using oil, more than I was comfortable with however, no smoke from oil cap, no loss in power.....just oil.

A compression test needs to be accompanied with a leak down test as recommended above. A compression test alone can be vague. Any competent shop can handle the test.

Good luck and look forward to your results.