in state of florida, is acceptance of partial payment by check with
"paid in full" written on check considered as obligation complete?

This may be of interest to you:

http://www.answers.google.com/answers/threadview?id=138600

The answer to this question may also help:
http://answers.google.com/answers/threadview?id=592669

Here is website that discusses "accord and satisfaction" in terms that
I can understand.  Scroll down to no. 3:
http://library.findlaw.com/2000/Jun/1/128424.html

ALthough this site seems to be 20 years old, suggesting that after
1985 the procedure explained will also apply in Florida, I would
assume that this is now the case.

Here is a recent Florida court case on the subject:
http://www.romingerlegal.com/floridacourts/court_opinions2/5D02-2105.op.html

And here is the Florida statute mentioned: 673.3111
http://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=Ch0673/SEC3111.HTM&Title=-%3E2006-%3ECh0673-%3ESection%203111#0673.3111

If that doesn't work, try here and click on chapter 673 part VI
http://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Display_Index&Title_Request=XXXIX#TitleXXXIX