You just need to get to the top of the transmission. Rather than go into a long, ale-soaked digression of how to get there, I present this link on interior removal/replacement. If you can get it to the pic in step 3, you'll have should have access to the bolts that hold the shift lever assembly in place.
If you find you don't have enough room at that point, then you get to pull the carpet and lift the transmission cover--then you'll look like this fellow--
http://www.chrispens.org/~kendall/clutchpin.htmlhttp://www.victoriabritish.com/interiors/t6/t6-guide.pdfGood luck, eh?