Product review (5 stars): Complete kit; so far so good, will check back in if the parts wear prematurely, but they seem quality
My dryer - Whirlpool Duet, model WGD97HEXW0
Problem - Insane squeaking - ended up being the idler pulley
Resolution - Squeeze is gone.  I replaced all parts provided here as recommended; did not notice wear on the rollers or belt, but have no desire to open it up again before needed.  I did notice some wear on the Drum Roller Axles, but at $15 a pop I left them in and greased up the new rollers.
Handy novice time - 0:45 - 2:30 hours (details below)

This had everything I needed for my Whirlpool Duet.  I have never performed Dryer maintenance before, but perform most house repairs myself, so am handy.  There are instructions that come with the parts, but obviously they cannot apply to every dryer model that these parts fit.  Due to a shipping problem with another seller, I ended up doing this repair twice; the first time I took everything apart, but after many days without a dryer, I greased the squeaky part and re-assembled it, which worked for a few days.

That first attempt took about 3 hours total.  I was moving slow and taking pictures of everything to make sure I could put it all back together (especially the electrical connections).  This helped a ton later on.  The second time it took me 60 minutes total - 30 to disassemble, 30 to reassemble.  This time also includes taking the dryer down off of the washer and putting it back up - a little difficult for me because this is in a closet with about 1" clearance on top of the dryer, so you could probably I knocked 10-20 minutes off the above.