Is there a less expensive way to get this done? Bear in mind I am extremely unhandy, although I am hoping to learn once I am not chained to the cube.
I consider myself a pretty handy guy, but when spouse and I cut a hole in a wall and installed an interior door it darn near ended the marriage (and my life).
I think this is one of those situations where quality (and marital harmony) is worth the expense. You could buy a pre-hung door with serious
installation insulation & weatherstripping, security deadbolts and frame, high-end electronic locks, and (if you want it) maybe even one that has an integrated pet door. (Like the electronic ones that respond to an RFID chip on your pet's collar.) Although installation is hypothetically straightforward, you'll be under very public pressure to finish the job promptly ("Hey, Dad, is it done yet? Can I drill that for you? What does that word mean?!?") and you might prefer to hand that off to a contractor too.
Otherwise I'd recommend the Family Handyman website:
http://www.familyhandyman.com/search?q=installing%20an%20exterior%20door