I have a bad shocker, it seems to be mechaically sound but I think it's low on oil - I reckon I can get a bit more life out of it by filling it up, maybe with a thicker grade of oil to give closer to original performance with the wear it will undoubtedly have.

unfortunately the haynes manual is as clear as mud as to how to do this -
Looks like the whole shock has to be taken apart (i'll use steel wire if I have to, or rope and screwdriver tourniquet style), but I'm wondering if I can slot a spanner on the top of the damper (where the rod goes into it) undo the top nut and pour in some oil, maybe some stp stabiliser or something, but without taking the spring out or undoing anything apart from the top of the damper.

PS. Oh yeah... whats the recommended fluid for these things?

Personally I'd not bother and upgrade to gas shocks!

how servicable are these shocks?, is there a replacable valve or something in there? I know the oil is replacable, what about stem seals?

I don't know with regards to replaceable inner parts as I think if they go they just tend to be replaced with inserts rather than be repaired.

As for refilling though I think you'd find it pretty hard to do it with the leg still attatched, plus, how would you gauge how much you needed in there and what if you overfilled it?

I replaced the oil in my last Volvo with engine oil and i'll be doing the same again with my current one once my lowering kit arrives! I used 10-40W full mineral in the last one and it worked a treat!

If your keeping things on a budget It's not such a bad thing. If you want to be fancy though, some nice Koni/spax adjustables and converted coilovers would definately be the way!