Was an access plate under the sink in my boat---really just a cut out to vent the alternator. I closed it up as I suspect your PO did. Not sure what you would wan there. You can get at the oil filter from the aft approach through the lazerette. I am assuming you have the W50.
I keep getting what is apparently empty messges from you on this site. Not sure what is going on. I suggest you go to the Tartan group site if you want to have dialogue. I may not be using this right--the messaging system seems confusing.