g2z24,
Welcome to the world of XJ's, I hope you have as much with your's as we've had with our's.
I'll give a slightly different spin on some of this advice. The rock rails are very important, as they both help you wheel and provide body protection. Bumpers are optional at the beginning, they add little functionality until you get onto much harder trails requiring lockers, etc. If you bang up the stock bumpers, who cares? You'll end up replacing them anyway. A good rear bumper is more important than a front bumper, because it helps you as you're dropping off of things.
Fender trimming is very simple, when you get your lift and tires on, see where it rubs and trim until it doesn't rub. Don't worry about how much, many of us have trimmed way beyond what you would think. I think bigger flares are unnecessary, some crack and break, unless you just really like how they look. The tires rub at the bottom of the wheel wells, not at the top, so opening up the wheel well with a bigger diameter flare is rarely needed.....just open it up at the bottom and run the stock flare. I run stock flares in the stock location with 35" tires and many hardcore trails.
Also, many '87 XJ's have a D44 rear end, which is a good thing......you may be lucky.
Ask around and get a lift kit that is highly recommended.....there is a lot of good experience around here. 32's are a very good tire choice to get started with, by the time you wear them out, you will probably be ready for more. After rock rails, a lift kit, tires, and skid plates, gears and lockers are next on the priority list, then bumpers.
Have fun,