VPN: What / Where to install in my network for max security?

Hello group,

I want to have access via internet to a intranet environment. For this I
think installing a VPN-server would be a good solution.

I have the following configuration:

1. PC: Linux box: Gateway to internet
|
Network Switch:
|__
| |
| 2. PC: Linux box
| Fileserver with Samba
|__
| |
| 3. PC: Linux box unused
|
Further Windows clients

Now I want to have access from outside (via the router) to the files located
on 2. PC (Fileserver).

Is it more secure to install the VPN-server on the 3.PC and from there to
access the files on the 2.PC? If yes: can I do that via samba or do i have
to install support for linux NIS/NFS etc?
Or is it better to install the VPN-server directly on PC2?
Is VPN actually the best solution for me? Or should I prefer FTP? If FTP:
Where in my topology for max. security?

Thanx for any hint!

Ciao
Tom