Joe,
A whole bunch of folks are going to jump in here. Most of them know their sh@t. What you need to do is look at what we suggest and sort the wheat from the chaff. Do yourself a big favor. Download all the manuals, and read them. Get to know your set. That way, if you need help, you can ask for help without saying, thing of a jig, do-Hicky, screw thingy or do dad.
I always start with a super detailed TI, (technical inspection). I know this set well, and would see things you won't. Thats unimportant. What's important is for you to find every gig you can. Write them down. Decide what is a show stopper, and what can wait to correct. If you haven't had a lot to do with this set, then look at it twice. If you find something later, add it to your list. This way you don't forget anything.
Turn the the set over by hand. Is the exhaust cap on? Is there water in the muffler? Are the batteries in the set. Are they charged? What kind are they? Is there oil and gunk running down the exhaust side of the engine? Look in the fuel tank with a flashlight. Are there signs of fuel, oil or coolest in the bottom of the set. Is the wire harnes intact? Or is it opened up all over the place? Missing parts? Lots of stuff I haven't mentioned. Read, read, read and read some more, the threads of those before you. Has someone tossed your set off a bridge? All the doors there? Weather striping? Are the fasteners all badly rusted? If so, get a sh@t load ordered to begin with, so you don't have to wait on them when you are done repairing the set. Take a sh@t load of good pictures, and post them in the forum. People here can see things you won't. Ask questions. The only stupid question, is the one not asked. On the other hand, don't ask ten thousand questions, because you don't want to look in the manuals. Understand that the manuals cover TWO different gen sets. So if you are looking up electrical parts, you need to know how to tell the difference.
Read, read, read. The -10 manual will give you lots of super good info. It's the one manual I would tell you to read from cover to cover. Many is the person who could not start his set, or make it produce power, because they didn't hold the S1 swith in the start position long enough. The -10 explains how things are supposed to work, in what order they are supposed to work, and what is supposed to happen, when. If you understand that, troubleshooting is MUCH easyer.
Now i I will turn this over to the guys who do this professionally. They are good. Listen well.