GU Clutch Actuation Issues

G'day Ladies and Gents,

I've recently run into some issues with my 98 GU 2.8. The feel of the clutch pedal has become very stiff towards the bottom of the pedal, almost feels like it's pushing against something immovable. I have recently had the master cylinder replaced as I lost the guts of it completely whilst on the road. Upon inspecting, the slave cylinder appears to have a slight weep, though still working. I'm now struggling to get the car into first gear from neutral when the engine is running, and also slight grinding when trying to get it into fourth gear. All other gears work when moving, though it has become more difficult and requires rev matching a lot more. When I do manage to get it into first with the engine running, the revs drop slightly, however not enough to stall the car. When the engine is off, no issues getting it into any gear. Due to needing the car on a public holiday, I called Lube Mobile with the hope that they'd be able to replace the master cylinder for me and get me back up and going. Unfortunately, they came out, knowing that they didn't have the part and couldn't do anything for me then and there, but still charged me $128 :/ . The dude said that although the slave is busted, it most likely isn't what's causing my issue and will likely require a decent amount of labour to get it up and going.

Does anyone have any ideas on what could be causing this issue? Lube Mobile seems to think it may be the pressure plate or release bearing, which will set me back a decent amount of money. I have a new slave cylinder on its way and I will be replacing that as soon as I get it. Fingers crossed that it's as simple as that.

I've chucked a video up showing the slave cylinders movement upon full clutch pedal operation, hopefully this may help.
https://youtu.be/hYykQmOms30 (New here and not sure if links like this are allowed, but here goes...)