You have to make sure you open up the necessary ports through your router. Default ports for MOH-AA are: 12201, 12202, 12203, 12210. I think there is 1 more, but I cannot think of it off hand.
If you do not know how to open the ports, contact me, and I'll walk you through it.
What is your DSL connection upload and download speed?
You can always put the sever on the "DMZ" port. This will not "protect" the box from prying eyes but is a fast way to host a couple of games and then move it out of the DMZ once your done playing MOH:AA. You will not have to worry about ports but your box will be exsposed to the internet.
Get the latest driver from Linksys, then set it for Dynamic Port Forwarding. This will eliminate the need for worrying about ports for every different game.
No. That's the point of 'dynamic' port forwarding. The router keeps track of legitimate requests (i.e. ones that originate on your end) and lets responses through. Linksys added this functionality in a driver update and it is great. It is simple to set up. I don't remember exactly but go into the router setup (i.e. 192.168.1.1) and look around for it. I think you just need to check a box. Kewl, eh?
What I meant is, just assign an IP address to each computer in your LAN and do away with DHCP. Unless I'm being clueless here, which is totally possible. But even if it is a little tedious to set up the ip's, if you play a few different online games it may be worth it. Especially since you will have the increased security that dynamic port forwarding provides, e.g. no unauthorized activity through ports that are permanently open.