rear main seal

My 2008 nautique has a little oil leak. I can't see where but my guess is it's the rear main seal. How bad of a pain is this job going to be?

I'm pretty sure it's engine oil. Is there a way to attach a photo?

Yes it's a rear main oil seal leak .unfortunately you will need to pull the motor its a chore if you are a novis mechanic like myself..

I was thinking I had a rear seal leaking on my boat, turned out to be a crack in the hose to drain the oil, the crack was right at the oil pan, replaced the hose and the oil leak was gone. I found the crack when I went to change the oil, after running the hose thru the bottom of the boat, I noticed the leak got a lot worse and found the problem to be the drain hose.

Definitely check the oil drain hose and also the hoses to/from the remote filter. When was the oil filter last changed and are you 100% sure the old gasket was not still there??
If nothing obvious then as mentioned above, clean everything up and tape some cardboard down to pinpoint the exact drip point.

The remote filter on the Chevy is a Ford piece, so it's the most likely fail point on that motor

Do you have an Excalibur or the 6 liter ZR-6??

If you determine it is the rear main seal it is not that hard to change and I would highly recommend running a National Rear Main seal, a Teflon if available. The Teflon seals are a lifetime seal good for a million miles. They come with a plasic installation tool you just slip the plastic over the tail of the crank and push the seal up and in with the plastic protecting the Teflon on the way in. Teflon is easy to damage on install but not if you use the provided plastic installation tool.
It will seem odd because the tool is large enough on one side to slip on the crankshaft and the other is smaller and fits in the seal. When you press it onto the crank the tool helps the Teflon lip expand up and over the crankshaft.
Put these in clean and dry. Dry because you want the Teflon to start transferring to the crankshaft. Once it does you have Teflon rubbing on Teflon and zero leaks for life.
They are a really cool seal, I have used several. They originally were designed to dry up leaking rear main seals on diesel engines. They work great.   NOTE: if your engine is reverse rotation they will leak, the Teflon is threaded for standard rotation.
I bet your 1998 has a standard rotation with the 1.23 drive reversing the prop only.
The tranny is much easier to pull than the engine. Pull the tranny or slide it back out of the way and install your seal.   Should be 2-3 hours work tops.   If my memory is correct the 343 is the older 5.7L engine?   If it is the newer 5.7L LS style block Fel-Pro offers the Teflon Seal for that engine if it is the older 5.7L vortec style block National offers the Teflon rear main seal. These are only available in full round standard rotation seals.

Here's the pic from Jan 10th to Jan 16th. I was able to get the cardboard maybe a inch or half inch past where the motor connects to the transmission. I'm going to take it to Jody at FL Inboards the first week in Feb.