Another tricky (IMHO) network configuration question

[alexzabr]

Well, I just acquired a network/wireless router(TRENDnet brand).
This is regular type; 1xWAN input, 4 Ethernet ports and b/g WiFi.
I have ADSL (DSL) internet line (through phone line) and ADSL - USB modem which is connected to my hoem desktop PC (through USB).
Now, with the router I'll need network-based DSL modem instead of USB to connect one to the router. It may take me some time till I acquite network modem, meanwhiel I'll be willing to utilize the resources I have at hand.
What I want: to keep my regular DSL - USB modem connected to the desktop, get the desktop's Ethernet (built-in on the board) hooked to the router (WAN) - i.e. my PC will act as an DSL - network modem.
Configure the PC and router appropriately to such setup and then get my laptop hooked by WiFi.

Manual I received with the router described the procedure of teh configuration bearing using DSL - network modem (not through the computer). The question is how the setup I want to build will influence the regular router-modem-PC configuration...?

Thanks in advance, Alex