Pop the spark plug out and pull it some more. If it's hydrolocked then the fluid will come out of the spark plug hole. Just swap out all the fluids, put in fresh gas, let it run for a while... it's not like it's a high performance, low tolerance engine... it might run a bit shittier than before, but meh, no big deal if you ask me. You may need to have the coils/windings cleaned, but most electric motor shops are shockingly cheap to have work done. Or just spray a whack of electrical contact cleaner in there... or even wd40... something to displace water and remove gunk. That being said, I wouldn't be too worried about the gas engine or alternator, it's the electronics I'd be worried about. Get it running, then find something that you don't care about and get one of your friends to plug it in, see how it goes. If it doesn't work, check for current off the alternator. If that looks good, then look for a replacement rectifier part on the internet and swap it in... you could even find something off-brand. If you're feeling really lucky, rip the electronics apart and look for something that melted or rusted, and try replacing it. I mean, it's only electricity and gas explosions... what could go wrong?