Finally, someone else who has heard of duramix. Some of the best stuff to use when it comes to attaching anything together that is plastic/urethane/composite. I used it to adhere my evo bodykit onto my tour'. You can check it out on cardomain if you want to http://www.cardomain.com/ride/2075887 .
This sort of bodywork is very involving but can be done. Usually cut the tops off of the bumpers you want to (just to get rid of the mounts and pices that go around the lights and grilles) and cut your bottom off and match the two. Drywall screws (nice and sharp)for temporary sets work well. I like to make sure my bumpers are flexable urethane so they don't break when they get hit. There are some books available at barnes and noble that may help. If you have any freinds that own or work at a body shop, you can learn alot just by hanging out and helping a bit.

95 Contour, Custom EVO bodykit, 2.0l, PNP Focus head, Stage 2 cams, Je pistons, Eagle rods, 4in1header, 2.5" header back exhaust(complete stainless), D P nitrous, ram air intake, 10mm wires, flamethrower.