Just my $.02...
When I plumb in anything, I operate under the assumption that I will replace from $fixture to the wall.
New disposer? Tailpiece kit, trap, nylon washer thingies where the sink drains connect.
New dishwasher? Hammer arrester, angle stop.
Toilet? Same as above.
I ended up with a small stock of parts I never used, so I keep them for next time. Inexpensive, and I have a spare X that I can't buy at 0230 when I wake up hearing a drip or some such thing. I'm also never stymied rummaging around for a mini mount flare washer and adapter when I just pull the stop off and sweat on one with the right fitting.
I am also *quick* to say "eff it" and go scorched earth. One repair kit on a faucet, and then out comes the torch. Go for warranty replacement if you can, but it's rarely difficult to convince The Wife to let me "fix" a fixture by just installing a nicer one with some feature she likes.
Oh, and another thing...
ALL flexible lines are considered disposable. Replacement < Deductible. If it's my washer hose and I just moved, inspect and reuse. If it's time to replace the washer itself, the hoses are trash. Same for faucets, etc.
Schedule a three day weekend with your two skinniest friends and PEX your heart out ASAP.