First things first, I've been told by numerous programs that having taken courses in a real classroom looks way better than online. Sure, it's more convenient, but it's also usually more expensive.
I looked at taking A&P through University of Phoenix and it was over $2,000 with no real lab portion. So I took a 3-credit course at a local community college WITH lab and it was only $600. Cheaper, looks better, has a lab, why the heck would you not go that route? I worked full-time on midnights in winter semester (3 or 4 days a week depending on available OT), took two 4-credit courses both with lab finishing with A's in both, did P90X 6 days a week and managed it just fine. Set your priorities straight and you can do it too. Not trying to brag here, I'm just saying you need to really buckle down because it's not easy to balance all of that.
As for sneaking into a real class, you are better off talking to the instructor or someone within the actual department offering the course like the program director, not just a secretary. I slid into a graduate level statistics course at a university while being enrolled as a post-Bachelor student. As a graduate student, it would have cost more, like about $1000 more, but I got a course override from the instructor because he has some empty spots he needed filled anyways. Give that a shot. It may not work out for you, but it can't hurt!