The last tubes I had from HPC had the cables attached but not the water tubes.
This is what I do:-
Turn the machine off (let it power down for a while just to make sure). Cut the red cable off the old tube about a foot back from the connector, do the same for the black wire.
Undo the clamps holding the tube.
Drain the water and clamp the hose near the tube, Turn the tube so the outlet is on the top and either pull the hose off the tube or cut it back (I tend to cut it as it will be a bit stretched anyway).
There will still be water in the tube so plug the outlet end of the tube and remove from the machine.
Put the new tube in place but don't tighten clamps yet. I found it is easiest to join the cable about a foot back from the connectors. I cut the cable to length, put some heat shrink on the cables and some silicon hose (this will be used after joining so push it down the cable out of the way).
Strip the cable back carefully and twist it together and solder the join, slip the heat shrink over the join and shrink, wrap with insulation tape for extra help and them slide the silicon tube back over the join. Depending in the power supply you may find it easier to trance the black wire back and replace completely.
Replace the hoses (I like to put a small cable tie on to hold in place). Remove the hose clamps and slowly fill with water if possible. Turn the tube so any air on the inlet end can escape (twist carefully so you don't put any strain on the connectors). Twist the tube back so the outlet is at the top (so any air can get out). This is the best position for the tube.
Move the tube so it is around 25mm from the first mirror and tighten the clamps - do not over tighten, the tube does not need to be unmovable just held in place.
Make sure there are no bubble especially by the output coupler - the latest tube seem better but some still get a bubble in the part where it narrows around the metal filament.
Make sure the water is running freely and carry out a test - if you are really lucky it will not need any adjustment, my last tube just needed a slight tweek!
That's about it - I don't think I have missed anything but just in case do not blame me if it goes wrong!!
Using two LS3060's and an ex 3020 user