For 1) - imho, there is no simple way to answer this question, because it depends on what you have in your current environment, what do you want to end up with, and how do you want to manage everything. For instance:
- How many users?
- How many systems?
- Are your linux systems in a NIS domain?
Multiple NIS domains?
- Will authentication be done from AD using NIS or LDAP?
- Do you use NIS for automounting and to serve other maps?
If so, will these be served by AD or by your NIS server?
- Do you want an open source solution or a commercial solution?
I know there will be people who will say "this is what you need to do", but what works for 50 users and 20 systems may not scale to 10,000 users. It all depends on your requirements.
For 2) - are you looking for login/logout times? Or per command activity?