Yeah, it is pretty easy. I was in same boat, went from 80 to 160 on my PB 1.67. The guides are a tremendous help.
http://www.xlr8yourmac.com is also a good place to gather a few tips...go to the page on PB hd upgrades and read some of the user reports. You'll glean some more hints and helpful advice on brands, etc. there.
What I found helpful is to get some mugs or cups out and place each set of screws in its OWN container along with a slip of paper that says where you took the screw from, or a drawing of where they go, etc. Piece of cake if you do that and no worries about losing screws, or [if you're REALLY careful] wrong screws in wrong holes.
Two caveats:
1. Don't do like I did and put one of the side screws into the external monitor cable screw hole. That screw is still there and it ain't comin' out.
2. Be very careful lifting off the top case...use a blunt plastic wedge screwdriver thing to gently ease it open from the right side to the left so you don't scratch your casing. Get a feel for the latches that hold the case on so you don't bend anything.
And gently ease it off starting from the front. so the case lifts UP in front of you just like it was the laptop lid itself. You can rest the front case on the open laptop screen; do this very slowly so you can see where the tiny plug is for the ribbon cable in case it comes undone in the process.
The rest is easy. Just make sure the ribbon cable is reseated properly and you should be in good shape.