Chuck here is a link with some good info on it.
http://www.goldwingfacts.com/goldwinghistory.htm
Several things at play here.
#1 You have to work with the budget you have for the purchase.This can sometimes get lost to others that have the newer bikes.
#2 As dawg said it is 22yrs old & that is low mileage. There is a theshold that happens with any motorized vehicle where low mileage isn't necessarily a good thing. However it still may not be a bad thing either if the bike has been maintained. See if owner has kept records of service.
#3 Do you have the ability to do some work on the bike. If so than a lot of that concern can go away.
#4 Things like timing belts (should be changed around 60k-80k), vacuum hoses, fuel lines, etc. can be brittle due to the age so that's why the guys mentioned it.
#5 I wouldn't let the alternator thing bother you too much unless you were going to load the bike up with hideous lights & such. Yes they were weak however if you are running stock it won't be an issue. There are also alot of used ones out there if it fails,the Compufire setup with Battery you can get at Wingstuff for $470.00 & if you join the VIP it will take off probably the cost of the Membership.Then you can buy other stuff at discounts.
#6 I think the stumbling issue was taken care of by that year but can be as BR said with the trigger wheel.
#7 You should just ask the normal questions you would if buying anything & be aware that you are buying a 20+ year old motorcycle. You will have work to do to it I'm sure but if the bike sings the "Ride Me" song to you & it fits your Budget than I wish you all the best.
Good Luck & keep us informed.