By the sound of it you're going to be better off leaving the oil lines alone. It looks like more trouble than finding the screw head.
I wonder if it's possible to push a tube of some sort into place that would guide the screwdriver into place within a bit?
I'm thinking along the lines of passing a bit of tube over the screwdriver and then guiding it carefully onto the screw, with assistance. Next, lodge the tube in place with whatever it takes, maybe cardboard and hot glue? Obviously a two handed job to hold the screwdriver whilst a n other is trying to fix the tube in place. Hot glue picks off most things with no damage, so you could go mad with it.
If it worked you could then probably find the screw head blind. Y' never know it might just work? Glad my bikes don't have carbs..
