Welcome to The Guild. There are tons of posts here covering the making of maps using various CC3 styles as well as Photoshop styles. The best advice I can give is to read through the tutorials subforum. Look at the first post in a thread and see if it is something that you like, if not skip to the next thread. Otherwise you could spend many weeks reading through all of them and you don't have much time. You could whip up something basic and use it temporarily if really necessary.