The concept of celebrating the birth of the Christ-child was around before Christians?
Yes. However depending on your pagan origins, it may be the return of newborn solstice sun, it may be the return of persophone (demeter's child) from hades), it may be the triumph of the holly king, etc and so forth. The decorated tree, the gift exchange, the yule log, hanging of mistletoe and holly, all these things and more pre-date Christianity and were incorporated into the early Catholic church as a way to influence others to turn away from their pagan ways and accept Christ (after all they have fun too).
As for the apples, nope, it connects to wassailing which is a pagan ritual.
"Apple tree, apple tree, we all come to wassail thee, Bear this year and next year to bloom and to blow, Hat fulls, cap fulls, three cornered sack fills, Hip, Hip, Hip, hurrah, Holler biys, holler hurrah."
So Christmas is almost 100% pagan in origins and rituals (even the Christmas ham). However, there's nothing wrong with adopting and changing customs and beliefs as they suit your religion, as long as you don't forget where they originate. Remember, the early Catholic church was all about converts and became extremely adapt at running mass marketing campaigns.