I'm assuming that the "ADD" you mentioned was stamped onto the dipstick when you checked it. That just means that if the fluid leven drops down to that line, to "add" more of that fluid to raise the level upto the upper line. As far as identifying the transmission, if it's an auto, use auto trans fluid (ATF). It should be able to use any dexron III or better fluid. If it's a manual, use manual trans fluid (gear oil). The propeller shafts just need grease in the u-joints. It's a good idea to switch to full synthetic fluids, but thats up to you. Standard fluids will work fine. If this doesn't clear things up, buy a repair manual for your truck. It will be your best friend for those little repairs, tune-ups, and adjustments that you don't want to pay to have done.
Try looking at
www.autopartsway.ca this is where i ordered most of my spare parts. great service.