New Clutch - slipping in top gear and under load

Hi
Just wondering if anyon'es had any experience replacing clutch cylinders before?
I've got a GS1150 Adv (2004 model). Had the clutch replaced 2 years back after a blew my drive shaft and hadn't ridden it much since. But I think I may have a leaking cylinder in the clutch. Someone said it could be the slave cylinder. Here's the symptoms:

* When in 5th / 6th gear, or accelerating hard, then the clutch will slip
* I've noticed a small drop in fluid levels in the hydraulic clutch reservoir

If I go the the "BM-TroubleYou" Dealer - he'll no doubt charge me upwards of €1k so going to give it a shot myself. So my questions (please help with any helpful advice) are:
* could it be anything else?
* What about the master cylinder?
* Is there a way I should clean off the clutch plates?
* Is there anything I should be careful of?

I've checked out YouTube but can find nothing on this particular problem - just changing plates.
Thanks guys for any help/advice
Cheers
Ben

Could be the slave or the seal the back of the gearbox, either way it's likely to need a full strip down to diagnose or clean up. When the clothes replaced was the whole clutch changed or jut the friction plate? There are step by step guides on here and it's not too difficult but can be quite time consuming for the first time.

As Steptoe has pointed out in some recent topic it could also be the gearbox seal in the clutch slave cylinder hole.
What color is you clutch fluid in the reservoir? If foggy, then it's the slave cylinder itself.

Br,
Jaak

Thanks for the replies lads. I will go check the clour of the fluid, but I think it was pretty clear.
The clutchplates were the only things replaced from memory.
I'll go check the fluid again now and give you an update

Pull the slave cylinder (easy with the swingarm off) and see if any gear oil runs out, if so it will be the input shaft rear seal. If hydraulic fluid runs out then the slave cylinder has failed, either way it's a strip down unfortunately and you will most likely have to replace the friction plate as it's going to have soaked up any oil and you won't be able to re-use, the pressure plate and cover should be ok but give them a thorough clean.
It's not a bad job to do if you take your time...you don't want to have to do it again soon!

Forgot to add, pull the starter and have a look in with a torch, you might just see some oil lying around..