I'm not sure what you're referring to about the relief of pressure - if you're referring to the 3 way valve dumping the water into the drip tray then this is the e61 group head - which as artman says - is entirely mechanical. There are e61 take-apart-and-rebuild tutorials trivially find-able.
Gicar make the controller for this thing too, and mine (I have a Minore-II) had the display die (machine still worked, but you could not tell the temperature as segments died one by one!). Rick Bond (coffee_machinist) supplied me one of the later blue LED versions that apparently lasts longer than the original.. They aren't particularly cheap, but I discovered just how impossible it was to source the seven segment displays Gicar used in that model! So I was unable to repair mine, which annoyed me a bit. But overall the machine is built like a tank
Service amounts to dealing with the seals and springs in the e61 and almost nothing else...Cheers
/Kevin

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