Ok, as others have said it is a dice roll, I have bought 5 or 6 generators from GL now (depending on how you count it as one is being resold as is). A couple would start up and run with only fluids, filters, and batteries, but all had some issues that needed to be addressed to be fully functional, this may be something like the bad aux fuel tank selector valve on the MEP-016d I recently bought (it also had 0 hours showing on the meter, but did really have some run time, someone installed a DC hour meter jumpered off the AC panel outlet), or it may be more serious like a seized engine, or missing control board, or somewhere in between.
As to the hours question, it is a dice roll, a low hour meter may mean a recent rebuild job, or may mean a meter died in the field and was replaced with a new one. A lot of people will pay a price premium for low hours showing, I know I fell into that trap somewhat on my recent purchase of the "0" hour MEP-016d even though I should have known better. My best advice on when looking at hour meters, first see if the mounting screws are rusted, if they are it is likely they meter was not recently changed, second when looking at GL auctions read the photo of the hours yourself, they often drop the decimal place in the text turning an 850.6 hour generator into an 8506 hour. Also avoid the extremely high hour generators, say anything over 4,000 hours (the rebuild schedule considers the 1800 rpm generators deployable at up to 5,000 hours, and the 3600 rpm units at up to 2500 hours). You may also look for other indications that the generator has been recently serviced, this may be in the form of data plates listing dates when a reset occurred, or like on my recently bought MEP-002a a stenciled "Serviced" and 2008 date painted on the side as a recently serviced somewhat higher hour generator may be better than a low hour one that has been sitting up for a decade or more with a seized injection pump.
As to the big question of price, it depends with location, in my area along the gulf coast prices tend to go up in hurricane season, but deals can still be found. On average for the last year or two MEP-002a's have been selling for $750-$1,200 depending on condition and whim of the market, MEP-003a's are a lot less common and seem to sell in the $1,700 - $2,500 range, somewhat more when mounted on trailers, I recently saw a nice looking trailer mounted low hour meter, single MEP-003a go for over $5,000 once you add auction fees and tax to the total. Having said that sometimes lots will sell off cheap, my recently purchased MEP-002a with 2060 hours showing on the meter sold for under $400, and others in the same batch sold for $300 - $750.
Previews can be good, I have rarely done them myself, ability to preview will vary by location, some sites are worse than others for parts walking off after the preview. In the best case expect to be able to do a walk around kick the tires, and if your lucky open up an access panel and peak inside, now that GL has started posting higher resolution photos I think the benefit of a hands on preview has decreased. Note you are not alone in thinking about buying a surplus generator after the recent east coast power event, I suspect it will drive up prices on these GL generators nation wide for many months.
Ike