Do not use a heat gun if you don't know what you're doing. A decent hair dryer will do it, but the main tool is a SMALL putty knife like 1.25" wide and some elbow grease.

It's not too bad, just keep pushing upward to break the seal in sections as you move down the length of the rail. It's a good shoulder workout. Use some common sense as you insert the knife against the cab and you won't hurt the artwork below the rail line at all. You will most likely have some leftover adhesive on the cab, but nothing Goo-gone can't help you with and some scraping. Try to get as much of the leftover off as possible, but it is not totally necessary to have it 100% removed.

Also be sure to use quality double sided tape. Something used for automotive body molding is good and can be found locally at auto parts stores for instance. It's usually pretty expensive there though. Terry at Pinballlife has great stuff that is priced right. I have seen some bad side rail jobs when people use sub-par double sided tape.