Thought I'd update this issue ---
To recap, there was some corrosion around the oil pump cover and some sludge in the area. The corrosion I assumed was from coolant leaking past the cover.
I thought I'd need a pump rebuild, even bought the seals to do the job, but instead decided to just pull off the cover and take a look. Whatever sealant was on the cover was long gone, so I just sealed it up again with RTV and put it back on. Since then, no sludge and no corrosion -- moral of story, the factory sealant doesn't last forever, so if you have leakage there unless it's oil from the weep hole you might just need to pull the cover, reseal and reinstall.
Hope this info I'll be of use to someone...
Van