P5 is an excellent engine. Probably no reason to get a new piston/sleeve unless that one's been scarred or has been pinched already several times. Having it squeezed is about $20 plus shipping. You might be able to find someone with a crankcase for it, or I've seen wonders worked with JB Weld. Might hold, might not. That's a Novarossi, but a Rex or Top crankcase should work. P5 has had at least 2 crankcase versions though so you'd need the right size one if you replace. If you can have the p/s squeezed and either find a used crankcase or repair that one and get it running it's probably worth it. If the bearings are bad or it needs a new rod then probably just better off with a new engine.
BTW, is that an RD Logics pipe? I have one of those in a pit box somewhere.