Check NADA Guides. This is the used car value site that many banks/credit unions use to figure out the clean retail price of vehicles so they know how much to borrow to a customer. That is the site I used to figure out the value of the 2011 that I just bought.
This! Of course, you can spend all the money you want on a vehicle, but if you're asking is it worth it. Make sure you know how much your vehicle is worth by checking car valuation sites in regards to your area. Not only is this important to lending, but also resale and insurance. I'm tired of people trying to tell me this FJ/or insert product here is worth more persay. Possibly to another enthusiast, but whoever is willing to pay $xxx amount is what it's worth. Besides say you pay higher and it's insured for it's book value, if there's a theft, you're the one that really lost out.
Just for comparison, I purchased my '07 at $14k for 110k miles. Book value was 15,250. So an '08 with 130k for $15k seems reasonable. If you want try to negotiate it further, research the things people have mentioned and scrutinize the car. Most likely bushings would need to be replaced. Springs sag easily on FJ's. Not saying you should, but the FJ usually has a driverside lean that you can mention *cough cough. When you accelerate, sometimes a un-lubed drive shaft will cause some vibration from a stop. This might be some things to point out.