Nozzle/butterfly assy: part # 34534 ($7.60)
jet wrench : part # 70830 ($30)
To remove the jetstream jet bezel, use two flathead screwdrivers, and simply pry it out. You do not need to remove the "eyeball" of the jetstream jet...it will come out with the bezel. If it's been a while, it's not going to want to come out easily... There's no other way to remove it... Just use two screwdrivers, one screwdriver on each side, and pry a little. Repeat... until it pops out.
Once it's out, dry fit the wrench to the new butterfly assy. This is so you'll know which end of the wrench to insert into the hole where you just removed the jetsream jet bezel. Fit the wrench into the hole, and fiddle around until you feel it lock onto the tabs of the old butterfly assy.
If you don't push very hard while turning counterclockwise, you run the risk of damaging the two "teeth" on the old butterfly assy that grab the wrench. Make sure you push quite hard while turning. After several revolutions, remove the wrench, reach in, and simply pull out the old butterfly assy.
When installing the new one, point the nozzle opening to the 6:00 position. You have a 75% chance of installing correctly, but it spins as you tighten it.... Any way use the wrench to tighten it. Simply pop the bezel back into the jet.
Turn on the jet, and test the function of the new adjustable jetstream jet. If you suspect that it's not working quite right, congratulations, you're in the 25% club that had the nozzle rotate out of position while installing it

Just rei-install the butterfly assy again, and this time, cross your fingers
Enjoy
~Swine