I am in the process of writing an tutorial on trigger valve replacement. Currently I only have one picture online of my replaced trigger valve on my Super Soaker CPS 2700:
http://www.sscentral.org/images/dscn0373.jpgYou'll get the basic idea from that picture, though I should download the whole image set from the memory card. The repair, of course, will differ from water gun to water gun depending on how everything is set up. This was actually a very extensive repair and what you see is only the final product. Parts of the case on the internal side had to be removed. I also had to fashion a way to attach the PC to PVC, and I found the best way is to use a 3/4" male threaded to 1/2" female pipe reducer. That however only applies to CPS PCs that have male ends (i.e. the O-rings are attached to the PC). The smaller PCs will have to use a different method.
In my post at Super Soaker Central I noted that this is much more than a modification. This is far stronger than before and I now can add essentially as many balloons as I want without fear of a break. The flow path has been changed to linear. The PC is larger than that of the smaller CPS water guns, so technically I suppose I could add an excess of 100 balloons, though I doubt that would really be useful. This modification/repair should allow for extended distance, so I would definitely recommend it.