What DSL modem should I have?

Recentlt bought Dimension 3000 with TrueMobile Broadband router.  According to the instruction, I require a DSL modem.  I already have a AOL broadband USB ADSL modem.  So does that means I need to discard the AOL modem, and then connect the phone line to the back of the TrueMobile router via a filter?  That way I still can use both phone and internet at the same time.  I have a wireless adaptor already connected to the Dimension, and a wireless card on a Dell laptop.

 

Am I right or am I missing the obvious?

 

Thanks.

 

Paul