I assume you will be doing the same type of fishing. bay or near shore.
I think 16' is minimum. 18' is nice. 20' is real nice. 23' is awesome.
Coast guard auxiliary runs a good class.
There are thousands of books on the topic.
besides pfd & vhf, you will need flares, horn, fire extinguisher, etc.
this is the link for the RI course materialsl.
http://www.boat-ed.com/ri/course/index.htm
There is a lot more you need to know. Keep asking questions.
Zac