Not done one for ages but IIRC I think there is a threaded insert in the block that the 10mm bolt screws in, if you keep turning the bolt it may undo the insert out of the block then remove it once the cover is off.

Can post the instructions for the belt, ideally you need a locking pin but you can get away without it if you mark everything up.

Also most should have been changed by now, but if any of the idler pullies are plastic swap them for metal ones, they used to be the main failure of these engines back in the day, end result is a scrap head as the camshaft and bearing caps snap!