I've replaced both sets of shocks on my truck. The front ddid require a spring compressor, but the rears were so easy they were a joke: 20 minutes and I was done. Mine was TRD so it came with the Bilsteins from the factory, but they are definitely a little more subdued than the types you'd order as direct replacements from AutoZone or NAPA. The stockers are real narrow and, from my experience, a little more plush than the replacements I got later on.
As far as Rancho Vs. Monroe Vs. Bilstein, I say Bilstein. Hands down. Well worth the money. For one, they use gas instead of oil, so they stay cooler and perform better under rough treatment. Plus (and most importantly) Bilsteins come with a lifetime warranty for the original installing owner. Good stuff.
I've now put over 100K on mine and they're still going strong! <img src="/forums/images/graemlins/kewl.gif" alt="" />