Vista - A few general Media Center questions

I just got an 16:9 LCD TV and plan to get a desktop running Vista Home Premium and install 2 tuner cards. I have a few general questions:

1. I get free cable from school and it is IRC, not NTSC or ATSC. Is there a way to get guide listings for my list of channels (likely unique to my school)? I remember from an old MCE I used to have that your options were only local commercial carriers. Is there a way to customize this if that is the case?

2. Since HD channels are 16:9 and regular channels are 4:3, how will Media Center display on my TV? When I change to a 4:3 channel, will the entire video display change to 4:3? (E.g. if i were to go to the Guide or My Music while currently on a 4:3 channel, would the Media Center GUI still be 16:9 or would everything change to 4:3?)

3. How important is the type of TV tuner I install? Is there a preferred type that will work best with Media Center?

Thanks in advance for any insight!