I'll borrow what I said in reply to this question.
In my opinion the quickest and easiest way to find a selling value for a guitar is to:
Go to ebay, and search the model.
Look at what the 'buy it now' prices are, or what people are bidding.
You could also check the small ads in the back of guitar magazines. 'Guitarist' run back page ads, and can be very useful in determining the value of a piece of guitar related gear.
Look at the prices individual sellers are asking for, and see how much attention auctions are getting at different price ranges. Look at completed listings (check the checkbox for 'Show Only - Completed Listings' down the left hand side, but you will need to login).
You can try asking a guitar shop for a valuation, but they are probably going to give you an estimate that is a little low, as they would be hoping for you to sell the guitar to them there, so that they can then sell it on for a profit later.
If I was to be buying a guitar second hand, I would want the electrics and neck in particular to be working perfectly. In a less than perfect situation, I could cope with problems with the body, bridge, nut and tuners, as I could sort them later (in a professional set up probably), but obviously I would prefer no major problems at all.
In order to improve the sale value of the guitar, get it properly set up and put on some gauge 9 or 10 strings. Include all that came with it, including any cases/spares. Get anything that is broken on the guitar mended, and check all the electrics and tuning heads particularly.
Hope this helps.