Here is how I do antenna replacements:
Remove Grille
Remove Driver's Side Headlight bucket (assembly)
Unscrew nut that locks antenna to body (on top near shaft)
Pull antenna down and wiggle until it comes out the hole in the bottom
Cut antenna wire off of old antenna.
Get new antenna from me ($12)
Tape old wire and new wire end together with something strong (aluminum tape,
duct tape)
Pull radio out and unplug old antenna wire
Carefully pull old wire into the car and this will feed the new wire in place
(it helps to have someone outside feeding the new wire).
Plug the new wire into radio and replace it.
Pull antenna up to proper position, and install body and seal then secure
with lock nut.
That is it.  Takes about 10 mins.

Note on antennas, I sell a cheapy antenna for $12.  It fits perfect and looks
excellent, and works excellent.  However it is made in Tiawan and some people
can get upset about this fact (what do you expect for $12?).  Or I can sell
you a new VW antenna for around $40.  Made in Germany.  The only real
difference I can see is that it has a feature that allows you to not only
push the antenna all the way down, but also lock it in the down position with
a key.  Pretty neat.  Worth the extra money?  That is up to you.  Just FYI.

Thanks,
Ken Wilford
Van-Again
John 3:16
http://www.vanagain.com
Office: (856)-765-1583
Fax: (856)-327-2242