Yes, those issues are relatively common unfortunately. They are also critical to get fixed ASAP. Oil leaking from the OFHG will get on the accessory belt and it'll slip off the crank pulley. Because of the design of the pulley it'll slip off to the back, get crammed between the pulley and engine block, and pretty quickly shreds of belt will get stuffed through the front main seal. That debris is now in the oil pan where it'll get sucked up and clog the oil pickup and starve the engine of oil.
As far as the price I really don't know if those are normal dealership prices since I DIY but I do know that you're much better off going to a well-reviewed independent BMW or at least euro specialist shop instead. Dealerships are for when you still have a warranty, otherwise they charge
way too much. Neither of these jobs is very difficult and they don't require any specialist tools even.
I highly recommend replacing the accessory belt and tensioner while you/the mechanic is in there and also upgrading the "mickey mouse flange" (about 21:16 in the first video below) with a metal one. I've upgraded that on 3 BMWs so far and every last one of the stock plastic ones was already deteriorating with 2 of them breaking apart on removal.
DIY for OFHG (different model; same engine so any differences will be4 super minor):
DIY for belt and tensioner: