polo 9n door speakers + double din headunit

hello

I would like to know how to take the front door speakers off as they are rivet from the factory and are on their way out and what size will fit in the doors or what measurements should I be looking for please. 

secondly, what size double din stereo will fit in the dash seeing on ebay there are two types 6.2 inch and 7 inch

thanks in advance.

Edited 22 January, 20197 yr by performancevw