Will Sat Nav Fit?

Hi all,

i have just bought a GT TDI 130 (3dr Black).

Will the Sat nav offered on a certain auction site fit straight in, and will i need to buy a gps unit or is it buit in?

I currently have a single cd and single tape deck.

I would also like to upgrade the speakers and install an amp but dont want to change the oe look in the dash. any ideas?
i was hoping the standard stereo or sat nav would have pre-outs.

Also will a cruise control unit plug straight in or is it a job for VW?

Also i ask too many questions:notworthy

Matt