OK, you have definitely come to the right place.
However, some of what these guys are telling you will get you hurt.
They are not doing it on purpose, but they still have not slowed down to your level.
You and they are on an intersecting course. You are learning what they are talking about, and they are beginning to realize how unknowledgeable you are.
Some of my work brings me in contact with people who have no idea about what I am talking about, so I am a little more attuned to it then some of these guys.
Don't worry, they will catch on quick, and so will you.
Just watch out for the humor, it runs fast and deep around here.
Here is the main thing they have left out without realizing it.
There are going to be times when you are doing a procedure that they recommend, that park will not work.
And usually its a procedure that will have you under the truck.
Which means that it can and probably will roll over on you.
For the next year or so, no matter what, when you start to get under that truck, chock the wheels.
Chock them good.
(Oops, I'm doing it too. Chock means block the wheels by putting something in front and back so they cannot roll. Cement blocks, a couple of 4X4 pieces of wood nailed together, something like that.)
The bigger tires will roll right over small chocks.
It would not hurt to make yourself some 4X4 wood chocks, or if anyone here has some pictures of what you use, post them so he can see.
Ropes tied to them will make them easier to pull out.
While you are on here, you will hear lots of comments about your front differential (front end), your rear differential (rear end), Transmission, and transfer case.
Don't worry about them. Your parts are good, solid, middle of the road, equipment.
There are stronger ones out there, and there is a lot of weaker ones out there.
Do not even consider any swaps at this point unless it is to swap the same parts to replace worn out parts.
Conversions are out of your ability at this point.
Keep hanging around here, and they will not be forever.
I think the guys here have what you have pretty much nailed down, but if you want to be sure, take pictures of these:
The front of the front differential. Squat down right in front of the truck and shoot up under getting the front differential cover.
Do the same at the rear, you want a rear shot of the rear differential showing the cover.
Right behind the blue thing behind your engine.
( the blue thing is the torque converter for the transmission, the thing with the teeth its attached to is called the flex-plate. Sometimes called the flywheel. The difference is not important at this time. Oh, and the flywheel cover goes over the blue thing and the thing with teeth.)
Anyway, right behind the torque converter is a flat squarish pan which is the transmission pan. A good clear shot of it showing its shape would be nice too.
The four hole things on the ends of the front and rear drive-shafts are called Universal Joints, normally called U-joints.
These are what they suggested you check.
I agree, but CHOCK THE WHEELS.
Also, look inside the holes at the round steel cap inside. Its called a bearing cap. It should be fairly dirty. If its shiny, and looks like it has been rotating inside there, that U-joint is either bad, or about to go bad.
The part of some drive-shafts that seem to neck down smaller and then get bigger again is called the slip joint.
The little part slides in and out of the big part to let the drive shaft change lengths as you go over bumps.
With the transmission in neutral, and the wheels chocked, you can grab both sides of the slip joint if you have one.
Some shafts don't.
You will probably be able to twist the two pieces slightly opposite each other. Also, you can probably push the shaft up and down and see some flex there.
A small amount is ok, lots of floppy movement very loose with possible noise is not ok.
Check back here.
I will stop here. Tomorrow, if I get a chance, I will try to copy your pictures and add arrows and comments to show you what is what.
J.