First and foremost, Auctiva is a listing tool - that's it's primary function, and it does it pretty well. You can also store your images online on Auctiva's servers. There is an added benefit of being able to list as many pics in your listing as you would like, without being charged extra (eBay charges extra for more than one pic). You can also schedule your auctions to list at specific times and dates at no extra charge (ebay charges extra to schedule listings). There's also a "transactions" console to help manage your customer interactions/emails/feedback/etc.
A bunch of other stuff, too. Feel free to poke around a bit and get to know the place. You can check here for some helpful advice:
http://www.auctiva.com/free_auction_software_help/help.aspx
Down at the bottom of that page is the link to submit a help ticket to Auctiva Support. They're very helpful folks.
Of course, Auctiva has a lot of templates to choose from, as well. Unfortunately, I'm not much of an expert, so I can't help you much there, but there's a "Templates" forum where you can post any questions you may have.
There's no need to cancel your eBay store! Auctiva's storefront is a great supplement for your eBay store, but it is not a replacement for it. Auctiva Store is basically a place where all of your eBay store listings and auctions are centralized in one place. You can also set up a blog there, or use the scrolling store window in your eBay listings to cross sell your other items.
It's a lot of stuff to learn, but just post any questions you may have along the way, and people will be happy to help.