I agree with BlackGT, rockers should be done first if you can. Just ordered mine

You can also buy bed liner in the can now, Dupli color carries it I believe if your local auto parts doesn't.

Once you have the rust gone, possibly your new rockers in, all your lines and such out of the way, one or two coats about 8-9 inches wide running the length of the rockers should prevent a lot of future problems. Some might not agree, but that's just my little spin on rust prevention. No one see's it and it could help you squeeze a couple more years out of 'em if you do it right.

Also, I don't have much experience with noise deadening spray on the outside of the car, but you can buy rolls of noise deadening material to go under your carpet, if you would rather go that route.