If you undo the battery holder and tilt the battery a little bit whilst its in place, you will get a bit more space. It can be done with the battery in position but very tight.
Honda fixed price is around 790 for the clutch at the moment. Not including flywheel.
If I was going to have this done I would do it at a Honda dealer.
Its an alright box to be honest. Theres always the debate as to whther to change the fluid or not. I have in mine and always hange it every 30k miles. Only use genuine honda fluid. Do not use anything else or you will screw it up.
The shifts should be smooth and quiet.