Audio Systems: should I buy any stereo for my car?, cassete player, factory radio

Question
   I have a 98 volkswagon my cassete player doesnt work, Im thinking in buying and replacing it.  My question is should I get it from the volkswagen factory and have to have them install it or would it be ok just to buy any other brand and have someone else install it.  Thank you

Answer
if you have the moonsom system is better to go factory also if you have stering wheell controls they only work with the factory radio and the color of the lights will be diferent if you go with aftermarquet is better to stay fatory i know the dealer wants over $300.00 for that unit

call this people www.oemautosound.com  they carry the same radio for about 100.00  
you also need two volkswagen keys to remove the radio and chage it your self this simple if you go factory  the plug will be the same and you save money
good luck