I need to change the side speakers on a 99 jetta but i have no idea where to begin, will apriciate any help

How many miles on the Jetta? Sounds like this can indicate a wheel bearing worn out...front brakes beginning to wear, any grinding sounds? Actually, a tire with a separated belt can also make thumping sounds while driving...Try for a free diagnosis at a small shop.

This is for a Jetta 99 to 05:
1999 2005 Volkswagen Jetta Side mirror Replacement READ DISCRIPTION

the problem could and most likely be a clogged catyletic converter.

You know you should have it scanned for codes.

If the bulbs and relays are good, then the switch is faulty.

If the door panel has never been removed then it could possibly be a bad speaker.

Being a 99 model it could also have a plastic liner under neath the door panel that has dry rotted and needs to be removed.

I'd place my wager on the speaker though.

If the panel has been removed check to make sure that you don't have any broken clips that attatch your door panel to the door.

Could try disconnecting battery for a few minutes.

Unplug the bulb and try the fuse again. If the fuse doesn't blow, replace the bulb.

pop the speaker grills out by using a small screwdriver, be easy don't want to ruin the grills, three or four screws should be holding each speaker, unscrew, pull out gently, for the side speakers, then disconnect speaker wires, for the rear speakers if you have woofers, the woofer pulls out from the trunk side, disconnect speaker wires before taking the woofers out.
when your ready to put new speakers in reverse the process.

I wish I could help you with that but I am about to change my speakers as well and I have the newer body 99 Jetta. what size are the door speakers for the front and the back? Thanks and I hope someone can answer your question....and if its not answered by the time i change mine i will let you know what i figured out!