Serpentine belt, belt tensioner pulley, idler pulley
 

I want to replace my serpentine belt, tensioner pulley, idler pulley. My truck makes an annoying squeeking sounds whenever its wet outside and I believe its the pully's and belt. Wouldnt this be straightforward? Remove belt, unbolt the 1 bolt from the pully and replace then put on the new belt?

Yup.
-Tighten the tensioner pulley bolt to loosen the belt.
-Loosen the bolt to remove pulley--then install new tensioner pulley.
-Loosen idler pulley bolt--install new one.
-clean all the pulleys w/ wire brush or scotch brite pad.
I just did this today--didn't help the squeaking at all.

Make sure you check all your pulleys for dirty/squeaking bearings; water pump, a/c, tensioner, idler, power steering, alternator. check for any play in the pulleys.
When the engines running look at all the pulleys for excessive wobble. crankshaft should wobble a little. Check you power steering fluid, I heard if it's low the belt (or maybe the pump) will squeak.
If all else fails and it's still squeaking, get a new tensioner--RockAuto has 'em for $40 + shipping.

Thanks, I will be a bit pissed if I change them and it still squeeks

Get Dayco brand if you can. And make sure everything has the same amount of ribs.