Reverse light switches tend to be very simple plunger designs. The reverse light switch is normally found screwed into the gearbox but may be attached to the gear linkage. Look for a one or two wire connector either on the gearbox or the linkages. Disconnecting the reverse light switch should (if in fact the reverse light switch is faulty) switch off the reverse lights. If the reverse light switch is screwed into the gearbox, replacement is quite straightforward but be prepared for some oil leakage as it is removed.
Dann, September 2007