Unless your car is low as fk u should be able to crawl under there on the gearbox on the drivers side there will be a thickish cable going in to a metal bit hanging off the gearbox, all the cables ive seen just screw off do this then follow it through to your firewall hole making sure nothings holding it down then yank your cluster out you should be able to detach the speedo cable from the gauge but be carefull they are delicate (speedo).
And theres a few screws but its all in there sweet!