Need Help - Looking to Upgrade DSLR

Looking for some thoughts/advice/help on taking a step up the DSLR ladder.

Let me first start by saying I'm not a photographer, but am interested in taking better pictures! ... If that makes sense!

We have a Pentax K-x DSLR with the 18-55mm kit lens. It took very good pics in auto mode when we first got it, but lately, and I don't know why, it seems like the pictures don't pop like they used to. They are still good, but they don's seem to stand out compared to our other cameras.

I recently picked up a used 35mm P5 body with several lenses filters etc. (for only $50) that are all compatible with the K-x. This was one reason I bought the Pentax - the compatibility with K mount lenses. Now, the older lenses are nothing to write home about, but opened up my options.

We'd like to get away from the 'full auto' shooting, take some classes and shoot using more manual settings.

I have an option to buy a Canon 7d with a 28-135 kit lens and only 22,336 clicks for $500 locally. Would this be a worthy upgrade? Seems like a really good deal.

Open to suggestions, tips, comments, criticism, etc. I value the opinions here (well, most of them :) ).

Thanks - Al