Salesmen, gotta love 'em.
He may not have told you the whole story. I'm not intimately familiar with your amp but I can offer some general advice to help get you started on your journey.
Yes, a "two zone" receiver can send a 5.1 signal to one zone and a 2.0 (stereo) signal to another zone and each can be controlled independently. Exactly how is somewhere in your manual. Good luck on that one.
But, as you've found out, you may need another power amp for that second zone.
All is not lost yet. Some 7.1 receivers allow the use of five of those channels for zone one and the additional 2 channels for a zone two application. If this is the case then you're all set. Again, your manual* has the answers to where you stand.
If not, then your original thought is correct. You'll need a two channel power amp for the second zone.
*Or, since you purchased from a local B & M, you might stop by and have the salesman explain how these things work on your particular unit. Bring your manual when you go.
Personally, my feelings on this "zone two" stuff is that if you need to purchase a power amp on top of your existing receiver, a separate two channel receiver would do the trick just as well. Heck, a Sherwood stereo receiver is available for under $90 at circuit city, J & R and, I'm sure, other places as well. A friend has had one for over two years now and, for what it is, it does the trick. And, DVD or CD players are a dime a dozen nowadays.