Having trouble with engine knock of 1992 ford f150?

I'm buy my first car it is a 1992 ford f150 everything is in good condition other then a knock in the engine. What is causing the knock is completely unknown was wondering if it could be dangerous and or what the knock could be?

Should I fix my truck or sell it and buy something else?

I'm a 17 year old male and I have and old Ford F150. I really like this truck. I prefer older vehicles. The body is really rusty and the frame is weak. It needs some mechanical parts too. The gas gauge just broke too. I know a lot about this truck. I've wanted one since I was a little kid. Should I try to fix mine up? Should I sell it and try to find another one in better shape?

Service Info missing from carfax?

I'm looking to buy a F150, and I found a nice 2008 F150. The dealership provided a free carfax. In the carfax, there were 2 owners. During the Owners history, you can see the oil change services that happen on a normal basis. But for the second owner's history, it shows one or two oil change services and a bunch of registration reports. The carfax states it was guaranteed by both owners there was no accidents, floods, structural damage, etc. The only thing that stands out to me is they replaced a rear wheel bearing seal during the second ownership, bed that was fixed at a Ford dealership. The truck has 105,000 miles, its a 2008, first owner was corporate, second owner was personal, first owner drove it for 20,500 miles and had it for 3 years, second owner drove it for 84,500 miles and had it for 4.75 years. I'm going to look at it in person, but from the pictures (a lot of pictures) the exterior and interior are in great condition. The engin compartment doesn't look too bad, can really tell from one picture. I showed it to my dad (has more car buying experience than me) said its a really nice truck, but he was the one who pointed out the missing service history from owner 2. But he does think I should buy it.

Heres the carfax link: http://www.carfax.com/VehicleHistory/p/Report.cfx?vin=1FTPW14V48FA12718&csearch=0&partner=GAZ_0

It looks like it just drove off the lot, not color matching issues, which is a little scary. But can I get other's 2 cents on what they think?

Transmission will not shift out of first gear - 1989 Ford?

I have a 1989 Ford F-150 with an automatic transmission, and lately have had some issues with it.

I had to drive 25 miles, and around the 20th mile I had to take an exit to get where I needed to go. The truck ran fine up until I turned onto the exit. When I turned on the exit, the transmission was "stuck" in 1st gear, and would only go 20-25 miles per hour. I ended up having to drive back home (20-25 miles) with it stuck in first gear, taking taking extreme care to be gentle on a back road.

The night before, the truck ran perfectly fine - nothing odd. It just all of a sudden failed. I bought the truck around five months ago, and has ran fine since with no issues.

We were able to get to a Walmart to buy transmission fluid. The truck is known to have a transmission fluid leak, but I keep a very close eye on the transmission fluids (check it with my oil - about once a week) to ensure everything is as it should be. As soon as I poured transmission fluid in, it immediately leaked back out onto the ground.

When I got back home, I had the truck towed to a garage for them to look at it. I originally thought it was a seal had broken, but the mechanic said that all the seals looked perfectly fine. He said he'd have to do more thorough tests (for $90) to find out exactly what is wrong with it.

Is there any ideas as to what is wrong with it? How much could it possibly cost to fix? Mechanic said could be pump or governor. Also, transmission made a loud thump when placed into drive.

Added (1). Transmission fluid is full, according to mechanic. As mentioned, entire truck (transmission and everything) ran fine the night before and that morning until we got around 20 miles away.