Standard Agile IRD-I: HOW Obsolete??

I'm not a satellite TV user (yet).  

I acquired a few Standard Agile IRD-I Videocipher RS units recently. 
I'm sure these are older units, but can these models still be used to
descramble satellite TV signals?

What other equipment would I need, at a minimum, to set up my own
satellite TVRO system?  I know I'd need a dish, but how LARGE a dish
would I need to work with the IRD-I?