Hi Tim...Trim can be pretty fun once you get the hang of it. Since you don't have to miter, you should (as you mentioned) fill the gaps with insulation, trying not to pack it in so tight that it can't do its job. Just a light fill will do, so no air can get in. After that, you should use a reveal of 1/4" (I think that's standard) or so in from the corner of the jamb (I hope you know what a reveal is because it's kinda hard to explain). Ok well set the trim back for a reveal and install it carefully, making sure to measure correctly and cut it SQUARE. A power miter saw that is set up correctly would be great. I would highly suggest drilling pilot holes in the wood if it's a hardwood such as oak or cherry, etc. as it may split if you don't. Just use a small drill bit and space it evenly around the trim, about every 12-15" or so. The corner blocks should also be pre-drilled to avoid any splits. The trick is to maintain an even reveal all the way around. Use a nail set to sink the nail just below the surface of the trim, as this will be filled later. After you stain/clear or clearcoat the trim, fill in any nail holes with putty or filler that matches the finished color...just do this AFTER you stain or you may not have a good color match. You can use construction adhesive to install the trim (such as Liquid-Nails) but I have done this before and any removal of the trim can result in losing some of the drywall, etc to which it's attached. That may be a bit of a hassle, as the adhesive can be messy and it takes a while to set, whereas nails will hold right away. I have done it both ways, and now I only use the nailing method since it's easier (in my opinion) to install and remove if necessary. If the door was installed nice and plumb the trim shouldn't give you much of a problem.