If it's an Auto TT loom then yes, it needs hardwiring in to the big plug (not sure about a manual loom, could be the same) This is quoted from the NA-TT thread -
'the big plug with the most wires in (6/7 wires?) has the reverse light wires in and these need joining to the reverse light switch. You just need to put 12v to each one until you get the right one that brings on the reverse lights, and the 2 thicker wires on the connector need snipping and joining together. The only other one thats used is the speed sensor which has the right plug on anyway. The ones that aren't used, we just tape up and tuck out of the way.'
There are some good pics and info on how to do it on this page - http://www.mkiv.com/techarticles/auto_to_6spd_swap/install_6spd/index.html