I'll jump in with some help.
The apple store has a good return policy, but you pay a 10% restocking fee. I don't know if that applies to everything, or just computers, so I would ask in the store.
The mini doesn't have an HDMI audio out. I have mine connected to multiple tv's via different video methods, but the audio method is always the same - minijack to stereo rca cable adaptor.
I am using 4 mini's right now for various entertainment related things - they are currently connected to:
42" LCD Olevia - connected via VGA / RCA cables (but I have had this one hooked up via HDMI cable using a DVI-HDMI adaptor from Radio Shack and it worked great, but using the VGA port frees up the HDMI port).
32" Insignia HDTV - hooked up via S-Video. This TV doesn't have HDMI, just component, for HD input. I have an external adapter for conversion to component but it's not worth the trouble for this TV.
24" LCD computer monitors (2) - hooked up via DVI interface
All of the systems work great. Most of the standard recommendations apply - install all updates, install perian, remote buddy is a great tool for minimizing your remotes, etc. I don't know what you are going to use for control, but my main mini system works great with the Harmony remotes.
Gotta run, but I hope this helps for a start.