[Ramblin Fever]

No need to feel intimidated by the never having worked on a car, in general.

This design of a tranny can make anyone feel intimidated.

Yes, you have the right idea. Park the truck on a flat surface, and starting with a COLD engine/transmission; i.e. after having sat for at least 5-7hrs, start it up and let it idle about 2-4min. Slowly manually shift it through the gears, allowing 7-10 seconds in each gear before putting it back in park.

You can check the ATF level with the truck in neutral OR park, on this particular transmission. I've always done mine in park, never had an issue after 13yrs.

Make sure you already have everything down on the floor with you, as you do not want that tranny getting too hot before you pull the fill plug. I want to say it's a 19mm wrench, can't remember off the top of my head. Very slowly pull this plug out, you'll get some residue fluid with it, but be sure to pull the plug all the way out.

If fluid trickles, you're good; but I doubt you're going to get any, so be ready to add fluid. Just start pumping away, some will come back out at you, so be ready and make sure you're not wearing any good clothes.

I always put cardboard down on my floor, along with some old towels.

Chances are, yes, this tranny might be toast. As aside from the fact they absolutely HATE being ran low on fluid, the fluid in and of itself is usually far past being spent at 90k miles.

Keep us posted. When you retorque that bolt, do not overtighten it. The pan is aluminum, you will easily strip/warp the pan.