I just resealed all the seams on my 96' Dutchmen this past fall after buying it and learning that it leaked even though the previous owner swore she was tight as a frogs bottom!
I also used Eternabond tape, I used 4" and the installation of it was a breeze, the prep work though was the majority of it. Although I will admit I may have a touch of OCD and anal retentivness...
1st I used a brush wheel on a grinder and removed any trace of the old sealant (butile rubber), I have an aluminum roof so I also ran it over the entire area the tape would cover to make certain it was clear of anything.
2nd I cleaned all surfaces to be sealed with denatured alcohol.
After that dried I immediately applied the tape.