Hello Naumanpak,
If by that question you mean "If I use connect a usb to serial converter, will I have to bother with USB code?", then no.
Suppose your computer does not have a native serial port, then you can use a usb to serial converter, and on the serial side it will behave like a boring RS232 port. You can just use something like minicom, hyperterminal, your own prog through ttyS0, etc...
But please note I only mentioned the globaltop part as an alternative that does not necessarily need a usb connection. This part gives you the choice to either use USB or use serial (rs232) for communicating with the gps part. I know I like the specs which is why I ordered 2 recently.
If usb is giving you problems (for whatever reason), it might make sense to look for something easier. And since this type of gps application doesn't really need 3452345 mbps bandwidth, why not go for a lowly 9600 baud serial if that makes your design life easier.
If you are still going the USB route and need something to take care of the usb part for you... like JacquesKleynhans said FDTI makes some good usb parts. Also cypress makes a couple of nice micros like the
CY7C68013A that takes care of all the usb fun for you.
hope that helps.