Several mechanical questions

Just picked up a 1999 GMC Sierra 1500 4wd Auto (V 6) with 180,000 miles on it. Before I put this into service, I'd like to get some things done and corrected, if possible. Here are my questions:

How tough is it to drop the trans pan and swap out the filter?

How tough is it to drop the diff plate replace the gasket and relub?

The gas gauge at the dash doesn't work. Is it most likely the gauge at the tank, or a short at the dash gauge?

The blower motor runs at only one speed. When it's off its off, but none of the other variables work until it get to the highest high fan speed. Is this the blower motor or switch.

With this year, model and mileage, what other fun things can I be expecting?

Thanks in advance for your reponse, I'll start browsing around and see if I cannot glean an answer on these inssue from other posts.

These trucks have a problem with the sending unit in the gas tank. Most guys/girls live with it and I just use the trip mileage...when it gets to 300 miles I fill up.
There is a fan speed selector called a resister pack located on the passenger side up under the dash on the air duck that goes to the blower motor. It's a bit of a job because you have to drop the bottom of the dash and there are screws that are hard to get to. The good news it the part is not very expensive.
With 180K miles who knows what the previous owner has had to repair/replace. Just have fun with it and when something breaks use the forum to figure out the best way to fix it.
:2cents:

Thanks. I figured out the blower motor resistor/relay from some other sights. The trip od will probably be the only choice. However, one other forum posted a reply that since my gaguge goes from full to empty randomly, that maybe it is a loose or rusted balck ground wire (?) If I can reach it without dropping the tank, I'll try. If not trip OD ! Thanks again