The 7950GX2 guide I linked to here is pretty good, it answers the tape question too - Click here.

It's currently only three threads below this one too :

Step by step (ultra short edition):

1.) Disjoin both cards and remove their cooling blocks.

2.) Remove the thermal pads from RAM and clean up GPU and PCIe switch (second card).

3.) Place one of the thermal pads (remove protection film on both sides!) on the voltage regulator of each card.

4.) Add thermal conductance paste on GPU, RAM and PCIe switch (second card).

5.) Install the aquagraFX block on each card. Use the bolts around the GPU at first and turn them evenly crosswise. After that you can continue with the other bolts.

6.) Place the seal rings in the grooves of the smaller block (the one with the laser engraving).

7.) Put both cards together and use the original bolts which came with the card.

8.) Check the connection between both blocks and make sure that no electrical elements of both cards are in touch.

9.) Use the long bolts (M3x25) to screw both blocks together.

10.) Install this monster in your PC and start smiling ;D