I was doing my clutch and replaced rear main seal and oil pan gasket while it was down. Lost the little oring for the dipstick but it was flattened and hardended some anyway. I found a replacement at local Ace hardware.
The pan can come off but you have to loosen the front differential drop it and or pivot it away. Then work the pan out best you can. Its not easy but doable. The windage tray wants to catch the oil pump pickup so you have to work it out just so. I had my trans off but have heard others have done it by itself.
I might clean the area and maybe JB weld or other if the gasket looks good and it looks like you can fix it that way.
Not that I know much but never really heard of it failing that way is crankcase developing pressure CDR ok ???
97 5spd K2500 Ext Cab short Bed ~160K miles.
TM, 3" downpipe & 4" exhaust, remote FSD, remote oilfilter, Gauges: EGT, Boost, Fuel Pressure, B&W Gooseneck Turnover ball, Prodigy Brake Controller. Hi-Temp Hydraulic Oil Cooler Lines.