I am confused as to how you want to hook this up
Internet -- prolink ---fe0/0(1841)fe0/1--pc
Or did you want the 1841 to be your primary internet router with the prolink behind it.
In any case a cisco 1841 is a commercial router which means it has many more options than a home router so it requires you to configure which to use.
To get a gateway and a DNS you can either manually enter them or you can set one of the interfaces to learn this via DHCP just like a PC would. To use DHCP to learn this you put in IP ADDRESS DHCP on the interface.
You more than likely will need to have a NAT configuration on your router also.