Interface Arduino with GPS & GPRS

Dear forum,

I need some help on the following interfacing issue:

I would like to know if i can connect both a gprs shield and a gps receiver(garmin foretrex 101 which uses NMEA via serial) on a single ATMEL ATMEGA328 Arduino Duemilanove board.

I'm working on my final year project and the aim of the project is the interface of a gps unit and a gprs modem with a single uController.

As I never used an Arduino board I don't know if I connect a shield on the board I'm "loosing" the serial connectivity for interfacing another serial unit.

Thanks anyway and sorry for my bad english

Stefanos