oil light on/flickering!?

you really need to read up --sounds like your engine needs cleaned up--& then tuned up-- sludge/gunk has built up-- it happens --who knows the usage of the motor---
The gunk spewing from the cooling system gives you an indication of the maintenance prior to you owning,

Not much--
Anyhow -- since you are now drinking-- read the threads/links on posted earlier & then look to any thread flushing out your cooling system.
Your radiator might make it it might not --but your engine block is full of crap .
Lawrence