Too Bad The Van's Not As Exhilarating As It Once Was. I'll Bet The Acceleration Is Suffering, Too.
A bad head gasket can leak compression, oil, and / or coolant. The coolant can leak into the comustion chamber or possibly the intake manifold and come out the tailpipe as steam. However, it could also leak into an oil gallery and go into the engine's crankcase and mix with and overfill the oil. A bad head could do this, also.
A bad gasket on an itake manifold could be the problem, instead. It will add coolant to the fuel / air mix and possibly wind up in the crankcase oil.
Anyhow, it will need to be properly diagnosed. Any running with coolant diluted oil is doing more damage to the engine. If you go anywhere with it to have it fixed, I don't advise driving it there.