5.9 Cummins oil leak gradually getting worse

[Sunbear]

Hi folks Sunbear here some of you might remember I have a 5.9 Cummins motor in a 36 foot blue bird 12-volt mechanical motor I've had an assessed at a mechanic told me its leaking from the o-ring around the camshaft above the rear main seal I was also told that I might as well replace the rear main seal when I cracked the motor from the tranny what I really would like is a place to do the work and someone is mechanically inclined to help me i have a friend in Flagstaff Arizona has both but it's kind of far away and really cold down there right now so I guess I'm asking for help or any instruction and I can gain I paid 18 for the bus and they're talking like 36 to 38 to fix it I ordered the parts and it was under a hundred fifty bucks