http://www.diynexus.com/vw/mk2_battery_removal/mk2_battery_removal.html
This link is for a Golf but photo No 4 shows the the battery hold-down clamp - close to the base of the battery. You wife's car probably has one similar to this.
If you don't have the radio code you might like to consider squirting 12V up the cigarette lighter socket to keep the radio alive while the battery is disconnected.
Peccavi
January 2009