Welcome to the board Barry
Now to try to answer your questions.
1) Not very current. Discontinued around 2000. Parts still available.
2) The seller should be able to tell you how the cabinet is configured.
3) A proper install would take most of a tech's day with training.
4a) Yes, DBS Manager
4b) Probably not.
4c) Cable is RS-232C. Probably not included.
5) Depends on the voicemail. Some are more money than others, some are more reliable than others, some have more features than others. A lot depends on the features you want and the name brand.
It also depends on the company doing the work. If it is a company that is known for quality work and has a good reputation, expect to pay a more. Find a good vendor and let them do it right the first time and everything will work out.
**Sorry, we cannot post prices on the open forum. Please send any pricing information via PM or E-mail**