Hi
@Nahkarankaisija welcome and nice car mate :)
I can answer/advise your first question.. and that's..
DO change the cam follower!! especially if its never been changed! once removed, you'll need to Inspect the tip of the Fuel pump too i'd be very surprised if you even have a cam follower left! if its worn right through, the HPFP will be damaged too! The earlier GTI's with the AXX engine (which I'm guessing is what you have) the cams and follower are prone to being beaten up, so do check this asap. if the follower has worn through and damaged the fuel pump tip too, chances are your inlet camshaft could be buggered too! If the cam chain and tensioner has never been changed then this is also something you NEED to do ASAP!
1st step is to inspect cam follower, then HPFP tip then inlet cam lobe! if all is fine.. then move to step 2 which will be replacing the cam chain and tensioner + the cam follower while you're there (or specialist whoever does the job).
I wouldn't chance anything like that mate. get it done and save catastrophic failure later on. Little worrying that your local "VW specialist" has never heard of the cam follower etc.
apologies I cant help with the Radio.