When removing and installing the seat, it is best done so with the passenger back rest removed. Just open the trunk and take out those two little screws and washers. If you area like many of us, you will probably end up doing this a few times per year for various reasons.
If you can...and, maybe another board member can help you out here...try to find some tapered bolts that will replace the four that are used to hold the seat to the frame. Someone sells them, I know, because I've had four for several years now...Just can't remember where the heck I got them. They make aligning the bolts and threads much easier so you won't cross thread them.
Finally, do something (duct tape, glue...whatever) to secure those 4 large pesky rubber spacers that are on the inside of the seat. If you don't, you'll end up chasing them all over the floor, or find them laying under your seat some place (if you're lucky) the next time you take it off.
As far as installing the Utopia....use a nice long sharp knife as was previously suggested...and carefully follow the directions.
Have fun and you'll be rodeoing with the best of 'em.