This will be my first attempt at making chocolate ganache for a cake filling. I have looked at dozens of recipes and some say it is important to refrigerate the ganache for at least 6 hrs before whipping, and others say do not let it cool past room temperature before whipping...What do you do?

It depends on the ingredients you use. I use heavy wh. cream, so I always refrigerate, at least for 4-5 hours, usually overnight . HTH

Im trying the recipe with only heavy whipping cream and chocolate.

my ganache i use 12 oz chocolate and 8 oz heavy whipping cream (along with some sugar and butter) let cool to room temp then refridgerate for 1 hour before whipping. Mine is not necessary to refridgerate longer than that

but generally, yes, you need to chill it thoroughly before whipping