Hi,
Welcome to FT. I'm sure others can contribute more, but as far as US Customs goes, I believe that will be done in Newark as I do not believe Quebec City has pre-clearance. After Immigration, bags will need to be collected for customs. Right past customs, there will be a "recheck" area to drop them.
Bags can almost def. be checked all-the-way through to at least NHL (not counting the brief "pick-up and carry" through customs at EWR). ...maybe even all-the-way, depending on CO's interline agreement with Hawaiian. I believe baggage fees are dependent on the first point of contact, so you will be paying in Quebec City as if you were on a CO non-stop flight YQB--> Hawaii.
Hope this (somewhat) helps.
Enjoy your trip!