yes, 140K is a lot on a 91-this car is older than your girl/boy friend...here is a glossary of terms you used:
you already know what the engine size and trans is, ARB airlocker is an after market differential locker that has been installed-it causes both tires to turn at the same rate, great for off road situations, not so great for you because you know this vehicle has had the differentials worked on-maybe professionally, maybe in the driveway of someones house-this is a minus for re-sale, the seller knows it
bfg all terrains are just a brand of tires, 33's are the height of the tire, this means he has lifted the suspension on the jeep, as 33 inch tires will not fit on a stock jeep in 91.
the super swamper is a different brand of tire which is on the spare rack-this means he probably had a set of super swampers on before the bfg's, and kept the spare when he got new ones...not a big deal either way
flowmaster is a brand of muffler, gives a vehicle a little more power, and is often a little noisy.
etc can mean any number of things
Here is what I see: this car has been customized, and it has a lot of miles on it, you should expect significant wear in all the drive train. The owner has also put some serious change ($) in the customized pieces, and would like to get some of that money back...so is this a good deal? For him yes, for you, no. At a wholesale auction, the modifications he performed will be a subtraction on the sale price of the vehicle. He wants you to pay extra for it-if you like jeeps, find yourself a nice stock used low mileage unit, less than 60K and not more than 8 years old, and pay the same amount.
Walk away from this one as a first car, the wholesale blue book on it is around 2500 in top condition, so the seller is trying to recover his costs big time-let someone else do that for him. Jeeps are soft on the market right now, find a newer one, with fewer modifications, and fewer miles, you will be glad you did.