That seems a little steep. But I know labor can add up real quick.
Sounds like you are fairly technically capable. Removing the engine isn't very hard just kind of a nuisance removing the bulk of the interior to get to it. 
Any reason you don't want to tackle it yourself?

You say crankcase, as in oil pan gasket or is it a front / rear main seal?
The front main seal would be fairly easy in boat.

Rear main would be a little harder removing the trans and v-drive but still do-able in boat. 

Hello!  

I've been a lurker on this site for about a year now but now it's time for my first post.  

Last summer we bought our first boat, a 2000 wakesetter with 500 hours.  Since then I've replaced the alternator, starter and a few other minor items. Now after it was de-winterized it appears that it has an oil leak from the crankcase.  The marina mechanic is quoting me $3700 parts/labor to pull the engine and replace all the seals (crankcase, rear main, oil pan).  Is this a reasonable cost?  

I'm debating if it's worth putting about 5k (needs steering cable and rear platform redone) into a 25 year old boat or if I should just sell it "as-is" and try to get a newer model?  

Any thoughts/feedback is greatly appreciated. 

 think there is any chance the bank would take a trade ??? asking for a friend 

That email also says "Shipping of the boat will be the responsibility of the customer".

Now to find one without brown interior, that is another story.

3 minutes ago, NorCalSurfer said:

My local Tommy’s said all sales go through M&T Bank. 

I'd be curious if this means you can get the boat just over invoice.