LIke David said, I bet that sink will clean up very nicely. I put a longer ("gooseneck") faucet on my galley sink and I love it. The original 1984-era, single-handle faucet had stopped delivering hot water. I replaced it with a two-handle deal instead.
As far as PEX goes, I'd use it wherever you need to replace broken stuff or where you're putting in updated fixtures. There's really no need to tear it all out. Mine's all copper, too. When I first got it the HW lines were split in a couple of spots. The local Lowe's had the adapters (in my case elbows) and PEX to replace the split line. Like you, I'm finding I have some places where split lines were replaced with garden hose. I'll get to that eventually.I also had to put some PEX in when I replaced that galley faucet. The new old line had corroded at the fixture and couldn't be reused.
Looks like a fun project - keep us posted.