Ha ha sorry guys, I think I might have over sold it as an easyish job
I am glad you've both seen a benefit in doing it though.
Regarding oil on the tensioner head when you remove it, I think that is just oil leaking out of the piston oil feed hole as you unscrew it.
I've got a cam cover gasket sat in my parts box as well, but keep putting it off. BMW warranty touch it until oil is leaking onto the exhaust manifold, so I might just tackle it myself for preventative maintenance in the summer.
Apparently the injectors come out easily on N57s, especially regularly used ones that are less likely to have rusted injector bores. Still need to get an injector seat cutting tool though. I've got the 6 x copper rings, which were a few quid each from the dealer.
Maybe we should get together and have a cam cover gasket swapping party