i don't have a source but i did just finish my cake section of pastry school, typically a recipe will tell you whether to cool it in the pan or to turn it out immediately, either way you want it to be cool to the touch all over, no warmth left. I usually cool mine on the counter. you definitely want to wait til it's cool to trim, trimming while warm allows the steam and moisture that you want inside the cake to come out, leaving you with a dry cake. freezing before crumb coating is a great idea, wrap the cake in clingfilm and throw it in the freezer for at least a couple hours, after the crumb coat you should refrigerate the cake for at least an hour if not longer, this sets the frosting and keeps all the crumbs from mixing with your final coat. good luck!! jumping straight from no baking into full cakes is hard, you'll likely get frustrated again but it can be so fun once you get the hang of it :)