The front main seal requires that you tear down the front of the motor. Heads and valve covers and intake stuff can stay in place. You have to remove power steering pump, a/c compressor (both these you disconnect from the engine and lay to one side with the lines attached), fan, timing belt covers, front engine brackets, timing belt (and all accessory belts - time to change them), and crank pulleys and sprockets, then pry the seal out and drive in a new one. You might take it to a shop and tell them to replace the timing belt AND the front seal, since the labor is duplicated for these and they have a flat rate for the belt.

I trace oil leaks by the clean and run method, using baby powder for a tracer. The powder will stick to the leaking oil. Good luck, it's findable and fixable unless something is cracked. From your description, my money is on the oil filter adapter or the front main seal or a front cam seal.

If you tear it down, replace the water pump.