1) Since the HW will change the Key will prompt you, normally you will have a 30 day grace period to re enter or reactivate windows on the virtual machine
2) Not necessary in any P2V I have done
3) No
4) Generally you should use ESXi(free) for hosting your servers and services but Workstation 9 or 10 can host them as well as player, VMware server is no longer supported by vmware or Converter.
The important thing to note if you plan on using player or workstation instead of ESXi, is to make sure the proper hardware version is selected. If using workstation or player, generally you want ESXi 5.x (hardware version 9)