Cat 3406E ID and front cover reseal

I have a 1995 FLD 120 with a Cat 3406E. Truck originally came with a 5EK, however, the oil cooler had a data sticker for a 6NZ on it. Several guys have said it is not a 6NZ, so trying to narrow down exactly what I have. Haven't been able to locate any stamp in the block. Can I have the data pulled on the ECM to get any more info? I do have the original serial number from the engine that was in the truck from factory. Any other ways to ID?

Engine has a bad oil leak in the water pump area of the front cover. Has been going on quite a while, but seems like it's getting worse, so it's time to just dive in and get it done. Trying to figure out what seal kit I am going to need. Have located quite a few, and not really sure of the difference. Any suggestions or part numbers from guys that have been there?

Have done some searching on procedure to remove the front cover, and I know I'm going to have to remove and reset the cam gear. Haven't been able to find any good videos or write ups on the procedure. Open to any suggestions or instructions.