It's a nice camera I have the same one.
I'd say you'd be fine with limited knowledge. You can still set it on full auto, and use it very similarly to a point and shoot. As you learn more about the settings you can increase the amount of manual control that you have.
As for the picture quality, it depends mostly on the quality of the lens that you buy. You don't want to cheap out on lenses. I've read a lot that the kit lens on the XTi is of marginal quality. When I bought mine I bought only the body.
Some useful basic accessories are a UV filter, polarizer, and of course a memory card (the camera doesn't come with one).
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