580k oil in rad

Checking fluids today and there is a thin layer of grey oil floating on the anti freeze, oil smells sickly sweet. But just prior to this winter I had a leak coming from middle left side of engine. it seemed like watery antifreeze, I couldn't locate exactly where it was coming from. I dropped a bottle of rad weld into rad, seem to fix leak. check rad over the winter and didn't notice grey sludge goo oil substance. Now I have a service manual and I believe it's telling me that the oil cooler and rad are two separate identities. But I have read in these posts that the rad/oil cooler share a wall separating the coolant and oil. Failure here results in oil being pressured into the rad cavity. My questions are. does rad weld end up floating at top of rad or would it dissipate into the anti freeze over time. and is it easy and more practical to put in an exterior oil cooler, or to pull rad/oil cooler and send of to shop, rad seems to be fine. Noting that I would have to reroute the oil lines to the new cooler and cap the old oil ports to the old cooler.

Thanks

580k oil in rad