The age is important here as some of the parts are now obsolete.
Can you send us a photo of the knob and spindle so we can ID the correct part Unless you can see it on one of our drawings,
Here is the link to the brushes
http://www.showerdoc.com/hydr-01102-hydra-sintech-motor-carbon-brushes-(pair)---in-brass-casing-01102
Yes this is the PCB for the AS 2000 http://www.showerdoc.com/TRITO-7072177-Triton-Pcb-Unit-7072177 You ask will it fit “this” shower you don’t mention what “this” shower is if “this” shower is a as2000 then it will fit.
http://www.showerdoc.com/trito-parent-188-triton-aquasensation-as2000t---as2000m-thermostatic-manual-power-shower
It needs a new solenoid valve http://www.showerdoc.com/shower-spares/triton/TRITO-82300430-Triton-Solenoid-Assembly---Power-Shower-82300430
Hi
These 2 screws are only retaining screws, they hold the inlet manifolds in place so they shouldn’t have any effect on the shower leaking.
It could be the mixing valve that is leaking, to check you will need to switch the power off and dry out the shower with toilet roll switch it on for a few seconds switch the power off again and have a close look to see if you can spot where the leak is coming from repeat until you find the leak.
We have this on offer at the moment which is the thermostatic version of your shower.
http://shower-warehouse.com/showers/power-showers/triton/ZTRITO-TAS2000XTHM-Triton-AS2000XT-Power-Shower---Thermostatic
I would strip out the filters and make sure that they are clean.http://www.showerdoc.com/shower-spares/triton/TRITO-PARENT-183-Triton-AS2000-manual-power-shower(Behind part 8 depending on if you have top or bottom entry)
I would start by checking the filters in the inlet manifold
Direct swap