[D15z8 gearbox capacity]

Does anyone know oil capacity of a d15z8 gearbox please? Got the car booked in for a clutch change but they want an extra £25 to change the gearbox oil at the same time, just trying to work out if this is good value for money or not 

 

Thanks 

[Clutch started slipping]

Thanks mate 

[Clutch started slipping]

Have recently bought a vtec-e sport and I got it for a pretty good price but the biting point was/is really high and has recently had a slave cylinder by previous owner so I suspected it needed a new clutch very soon, didn't think it would be quite this soon though.. Clutch started slipping on the motorway this evening..probably because of the 5k rpm fun just before that 

Any ideas roughly how long these will hold out for once they've started slipping?