I have an installer telling me I have to have the NT7B75AAAE which is the card that supports caller ID. Do I really need it?
Well, do you want (now or in the future) caller ID service? If yes, then you need a caller ID card. If no, then you could opt for a LSDS line card. This assumes you are using POTS lines for CO service. Not all providers send CLASS data by default, and some charge for the service, so you need to see what your provider offers.
How hard is it to program this phone system? Can I do it with a PC? Any special software needed?
Based on this post and your one other post in the CS1000 forum, I would suggest that you have a tech program it and give you some in-house training to maintain it.
Can you use a PC? Yes. Do you need special software? Yes, if you use the PC. You can also program it from a display set.
Since you provided no information on your software and very little on hardware and nothing on application, your question, is it hard to program? Well, I would answer that by saying to program this type of equipment to make the best use of its features is hard if you have no background in phone equipment, which is why so many responders in this forum make a daily living installing and programming this type of equipment.