I have a Honda EU2000i generator, and love it. It's a real workhorse and does everything I want it to except for maybe running my AC (and there are varied opinions about whether or not it can handle a 13,000BTU AC unit). It weighs about 54#, so I can lift it and move it short distances. It cost me about $900, but I shopped around. I think they can run as much as $1000.
I don't have to service mine as long as I use it properly. What I've learned is that gas will go "bad" fairly quickly and cause all sorts of trouble with it, so whenever I add gas I also add a small packet of liquid gas treatment (costs about $2 at my local lawn mower shop). Before I knew about what gas does to a generator I let it sit for too long and it fouled the carburetor and I had to have it cleaned (an $85 job). I was advised from a long-time generator user to actually let them run dry before storing them. That way there's no chance of gas fouling anything, and running it dry won't hurt it. I've left my sitting for well over 6 months and when I went to use it I added some gas and it fired right up.
What I like about my generator is that it's quiet -- really quiet. If I'm running it at the back of my trailer and someone stands at front you can't hear it. I also like it because it's portable. I can manage it. My trailer doesn't have a specific place to store it, so I have to lift it in and out of the trailer. It's manageable.
I know that Honda makes a 3000 model that would run your AC without problems. It weighs just over 100#, and operates much like my smaller generator. You might want to check them out. Yamaha is also a good brand, and there just isn't much difference between them -- personal preference, I guess.
Hope this helps.
Laura -- and Jed