TightVNC remote install and set it up as service

I am planning to install TightVNC remotely on PCs outside the office (running XP Pro). These PCs are scattered in different areas, farthest being like a thousand kilometers away from my office.

I would also like to configure these remote PCs’ TightVNC as a service.

Is there a way for me to do it remotely? I would like to do it without asking help from the users.

BTW, It’s going to be a VNC-over-VPN setup.