More info on that F-250???  7.3 IDI Diesel, 351 or 460 V8 gas, auto, 4x4, crew/regular/super cab, XLT, XL, Lariat, etc??

Would that be a steel trailer, steel frame aluminum skin, all aluminum?

Just remember, that package is turning 16 years old. I know it's only got 54000 miles but it is 16 years old. Myself... I couldn't pay that for the truck and trailer as a package....

Any time you are considering a 15 year old vehicle, it will be more of personal decision than any kind of value set by a industry book of values.  Just a quick look on Kelly's Blue Book shows 95 Fords with that mileage at $5000  A search on this website didn't have any 95 sundowners, but the few 2H, GN trailers in that age bracket were also in the $4000 to $6000 range.  

If it's extremely clean, Maybe it's worth $12,000. But if you are going to buy something that old, You might as well look for something that is GREAT deal. Even with out the miles, time will age parts and you probably will need to replace some items.  All belts, tires, hoses are subject to needing replacing. At 54,000 original miles, The truck may be about ready for a brake job, ball joints, and other normal wear items.  Even just sitting in a barn, it may need a radiator and transmission flush. 

If the set up is somethjing you like, Offer them a price and see if they take it, Knowing that you will probably have to spend a thousand or maybe two, going through everything.

you can check the value of the truck at edmunds, kelly blue book or NADA guide online, but you'll need more information than appears in the ad.

It may be worth the $12,000 they are asking. But you will have to go look and discuss it with them.

See what kind of preventive maintenance has been done to everything. How old are all the tires. If they are more than 5 years old, even with lots of tread left they will need to be replaced. Same with the belts on the engine. When was the last tranny or radiator flush, stuff like that.

Any vehicle that is 15-16 years old will need some repairs as you start to use it. The price you pay to buy it, will not be the total cost of ownership.  Look at your budget and be prepared to spend a few dollars here and there to fix the occasional part that just got old.

Even with a few repairs , it still cheaper than paying $60k for a new truck.

have a mechanic check it out and get  a local opinion of someone who can look at it.

Here is MY opinion on the truck and I have been in the USED car/ truck buisness since 1983 and the last 12 year dealing mainly in 3/4 ton and larger trucks.

No matter what book people tell you to look at the price is not worth the paper it is wrote on for older model trucks for sure.  Even newer model prices are off one way or the other.

Any way the truck:  with the list of options you listed and if the miles are correct the truck is worth around $3000 to $3500 wholesale and would retail for around the $5000. range, but it has to be NICE and rust free!  Sorry I can't help you with the trailer.

First off the exhaust leak is common for the 5.8L trucks.  The manifold is more than likely cracked, when the truck gets hot the noise is not as bad.

Second with 3.55 gear and pulling a trailer of any size you will need to make sure the overdrive is OFF, which will make the fuel mileage even worse.

My though: there is too many NICE trucks and trailer being offered right now some newer some older but do not get in a big rush and buy something you will hate and by the sound of this set up you WILL HATE it after you get it home and loaded....  Another thought; if you are looking at gas trucks and like the Ford, find you a truck with a 460 in it.  You will have plenty of power and in the long run the fuel mileage will be just as god if not better than the 5.8 truck is.  One reason is the 460 truck will more than likely have the 3.55 gears and you will be able to run with the overdrive ON, plus with the 460 you are not having to stand on the gas to make the truck move like you do with the 5.8 truck.  I use to run wreckers with both engines (before diesels got so hot) and the 460's always offered more power and better fuel mileage.