First, you need to empty the tank. You can run the pump, by connecting a +ve lead to the top pin. And -ve to the left hand pin. Disconnect the return pipe, centre, and the breather pipe, left. Also, remove the petrol filler cap. Connect a pipe in the system to take the fuel away. I used a banjo connector from a Mk2 Gti fuel pump, with the check valve removed. It is the bit between the yellow pipe and the MH. The breather pipe, on the left, should be blown through to make sure it is not blocked. You need to remove the locking ring. Haynes say you can do it with crossed screwdrivers, or, pipe grips. I made this, cos. Haynes is wrong, believe it or not. Audi use a tool, VAG 3087, that is not as pretty as mine! You then have to disconnect: The accumulator connection. The return pipe connection. The wiring connector to the pump. You then have to unlock the retaining ring to release the pump from the housing in the tank. Some jit's been in before me! Smashed housing, at the left hand black arrow. Broken retaining ring, at the right hand black arrow. You need to turn the retainer via the four slots. Blue arrows. Audi use a tool to do the job. VAG 3214. It's prettier than mine, but not as cheap. Start with a 110mm, 45 deg, soil pipe elbow. Cut the ends off. Accurately mark out four equidistant (nice word) lugs, a tad smaller than the slots in the pump retaining ring. Cut the lugs accurately. Together with the other end you cut off it makes a perfect tool. Stick it in the tank with a strap wrench. And, Bob's your Uncle. Oh! You'll need one of these. It's as dark as hell in the tank!