Topsider, http://www.westmarine.com/webapp/wcs/stores/servlet/SiteSearchView?catalogId=10001&Ntx=mode%2Bmatchallpartial&keyword=Topsider&Ntt=Topsider&N=0&y=0&x=0&storeId=10001&Ntk=All_2&ddkey=SiteSearch

Or just go to www.westmarine.com and type Topsider in keyword search.

Then you need the proper tool to remove the filter. I'm not sure which tool you need. Filters and the tool no doubt available on this website under Buy Parts.

Changing Oil and filter is very very easy. Either use regular oil or synthetic oil.
Change frequency is up to and your driving pattern.

How do you know when it's time to change again. I think you can figure out a way to remind yourself.

Is it economical? Dealer charges 200 to 300 bucks. I don't know where you live, buy my local dealer oil change is $47.00. So your cost would be what
8 qts at $2 = 16 + filter 7 = 23 bucks.

Steve