You have to remove or drop the axle, be mindful of the rubber brake lines, and Soak the Axle bolts with Pb-Blaster or CRC-Freeze off a day prior to allow it to work, then Spray it with in 30 minutes of working.
Use 6pt sockets and the axle bolts have been known to break, a impact wrench may be a good thing as the hammering action and torque will break the nuts loose.
There is a recall on those model years for the fuel tank, so you might want to have it looked at a vw dealer and if it qualifies as it hasn't been replaced yet you might get it done for free.
Build Years/Makes/Models: 1987 - 1989 VOLKSWAGEN CABRIOLET
UNits affected: 7500
Recall Number: 94V065000
Summary: A CRACK CAN DEVELOP IN THE FUEL TANK ADJACENT TO A SEAM WELD IN THE REAR OF THE TANK.
Consequence: FUEL CAN LEAK FROM THE CRACKED FUEL TANK WHICH COULD CATCH FIRE IN THE PRESENCE OF A SOURCE OF IGNITION.
Remedy: DEALERS WILL CHECK THE VEHICLE WITH A SPECIALLY DESIGNED TOOL FOR THE PRESENCE OF A TANK CRACK, AND REPLACE THE FUEL TANK IF THE DEFECT IS PRESENT.
SYSTEM: FUEL; FUEL TANK.VEHICLE DESCRIPTION: PASSENGER VEHICLES.NOTE: IF YOUR VEHICLE IS PRESENTED TO AN AUTHORIZED DEALER ON AN AGREED UPON SERVICE DATE AND THE REMEDY IS NOT PROVIDED WITHIN A REASONABLE TIME AND FREE OF CHARGE, OR THE REMEDY DOES NOT CORRECT THE DEFECT OR NONCOMPLIANCE, PLEASE CONTACT VOLKSWAGEN AT 1-800-822-8987. ALSO, CONTACT THE NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION'S AUTO SAFETY HOTLINE AT 1-800-424-9393.