1) Along with oil, change the oil filter. The fuel filter, cap and rotor, and tranny fluid.
2) For about $10 more than a "fake a lake," you can get a flush kit. http://www.overtons.com/modperl/overtons/detail/pdetail2.cgi?r=detail_view&item_num=25608&fcat=2C2 C
If you have a 1" input hose, you can use this one. http://www.overtons.com/modperl/overtons/detail/pdetail2.cgi?r=detail_view&item_num=25604&fcat=2C2 C
I don't have either, but I wish I did. Climbing under your boat, trying to hook up the "fake a lake," gets to really be a pain.
3) No info.
4) Just get some good quality teak oil. I hadn't touched mine in almost three years. I put some oil on it, and now it looks new. I used three coats The first one took a while, but then it was much better after that was done.