AT_HOME PRINTING: By far the most accessible, this is easiest option for tackling the project in smaller chunks on weeknights rather than spending hours in a studio or waiting at a print shop. However, you should test paper before buying a ton of it, printers can be especially finicky, and your can't exactly change the ink your printer uses. If your printer isn't higher end, you may have very limited paper options. Here's a little more on at_home printing.
ADDRESSES: You can choose to address your invitations by hand, or you can decide to print labels. Don't let the WIC bully you into thinking your own handwriting isn't good enough, or that the convenience of labels is tacky. As for the actual addresses, here are a few tips on how to address invitations formally, accounting for a whole host of last name conventions.