I've been looking after this Golf for someone while they're in NZ, don't want to give it back to be honest.

Just failed it's MOT for the NSF shock absorber strut excessive fluid leakage. Indeed, all the caked on mud looks wet around it.

Picking a new one up later for £45+vat and gonna be changing it myself this week. Is there anything I should know about that isn't covered by Haynes?
Can't find anything in the forums about changing them apart from one person mentioned this has been an old MOT testers' trick in the past and that they are gas filled not oil?!?!

Cheers for the help.

Car is a 2004, 1K, 2.0l GT TDI Sport, 103kw, BKD engine.

Ta, Sly.