I found I could change the near side gaiter in-situ when mine
failed the mot a couple of years ago. Fairly straightforward.
I recall thinking that I could probably do the other one from the
same nearside access, but bit more of a reach.
There's no fluid inside these, they are dust covers, so as Stuart suggested, a patch to fix
a pinhole would appear acceptable. Even a small dollop of CT1 might do, after good cleaning.
If your fluid is still red, or even slightly off-red, it's good. You should get a reasonable
indication of state by visible debris in the reservoir. I would change it by several evacs/top ups
of the reservoir. Doing it this way avoids getting any pesky air in the system.
N