White and black slimey rocker cover

Just started to look at the 2.5 N/A engine in my IIA 109 - it run's fine so it just basic maintenance and checking everything that I can easily get at. First stop the water - ohh and there is oil in it. Second stop the rocker cover - nice white and black slime. I'm guessing it's not been serviced for many years, but is it head gasket time or should I just give it a good service, replace the coolant and see what happens?

Those are signs of the head gasket, how do you know water is in the oil?.
It could be that those signs are remnants of a past gasket failiure, you say the engine runs fine.

whats the oil on the dipstick like? drain a bit out the sump that'll tell ya for certain if theres water in the oil, if it aint run for a while it could be condensation

change them flush them run it up and do a bloke test with the color change fluid tool and see what happens

it could just be condensation where she not had a good run or badlly maintained for years

Bloke test?.
Please explain pob's, in 20 years of messing with motors I've never heard of that.
Is it a nickname for a hydrocarbon test, for checking combustion gasses in't th'oil.