I use the part set function on Bricklink - you can do the same if you've kept the sets intact, just remember to manually remove the minifigs and any of their accessories that you will not be uploading from the editing page that will pop up for you in the part set process.
Making a few small orders first is a good plan - it'll get you familiar with the process as you mentioned, and it'll get you a few feedback points to start with, which will make some buyers more comfortable with you.
Before you upload anything, make sure you have your filing system set up and the parts you're about to upload already filed. Nothing is worse than getting orders for parts sitting in a jumble on your "to be filed" table.
With your eBay selling experience, learning Bricklink will be simple enough - a few differences, a few things that work better and a few things you won't like as well. The forums there are shark-infested, but simple start up questions generally won't get you bitten (or you can always ask here in safer waters).