So far the sequence looks like this:
1. reboot (to kill off any processes)
2. uninstall old vpn
3. reboot (to kill off any remainings)
4. install new vpn
This is working well when VPN was not used by the user. However, when it have some changes in its configuration (like choosing a hub to connect to) - it's still the old version after step 4 and I don't even know how to look for a solution. If anyone could help I would be greatful.