You didn't say what your skills are (if any) so I'm going to assume you don't have any. BUT, I'll assume you're handy enough to give it a go, to a certain extent.
Going w/all that, you might want to consider having a pro do the rough-out work. Since you'll need a header, special care would need to be taken so you get it in right. And if you're installing the door where there's brick and/or block and/or siding involved, you may need more skills than you have. Once the rough work is complete (per the specs of the pre-hung door), you can follow the enclosed instructions to install the door. DO read them BEFORE you or anyone else starts hanging the door. You may need to buy additional material. Also, with the rough work, there may be wiring or plumbing that needs to be moved. Again, the pro can do the move along with the rough work.
Price out the job in its entirety and price it out to just have the rough work done. If the difference isn't that great, well, have the pro do the whole job. My best to ya and hope this helps.
PS: I could be way off in assessing your skills but understand, I made a couple of assumptions and made my comments based on them.