Well, it depends what your HD camera records in! Most HD cameras record in a standard MPEG2 format, while some of the newer hard drive based ones record in AVCHD.
Not all editing software will allow you to work with AVCHD, but you also need to make sure you get editing software that is capable of editing HD.
Sony Vegas and Adobe Premiere Pro are a couple of the most popular ones, but make sure whatever software you go with, that you get the latest version, and make sure it supports HD.
Video editing is video editing, so if you know how to edit SD video, it should be anymore difficult to edit HD video.
Also, you will need a pretty decent and powerful computer to edit in HD, so make sure your computer is up to the task also!