How can new molar crowns be "adjusted" to raise them to correct front teeth from hitting, as front teeth did not hit before ? will onlays be required?

Remake them?: If the new teeth are out of contact, something must be added. Onlays are one option. Some material can be added to the opposite teeth, or even to the new crowns. I would not recommend grinding the front teeth. You could remove the crowns if not permanently cemented and just have the lab add to them.

Several ways: Problem is occlusion. First way is to remake the crowns. Second is to have your dentist refer you to a competent orthodontist who has experience with adults. Third choice is to use a night guard and retainer combination to maintain if you are able to chew normally. The appliances will protect your teeth and tmjs from bruxing at night while asleep until you can make a treatment decision.