I'm familiar with the Citroen Hydrophenumatic system, I built a rather nippy BX 16V, I think you'd have liked it if you like your cit's. Hydraulic systems are a bit different to gearboxes. As I've said above purely IMHO I wouldn't use it.
TBH as you don't want it spitting the contents of the gearbox onto the floor I'd say it was worth doing, 14quids worth of Semi-Synth Rover MTF and that includes a spare half litre bottle just in case ;-).
Cheers Matt