Getting familiar with this change will be easy. ATIS gives you the altimiter setting of your landing airport so at 18,000 feet set it. Unless it changes significantly ATC never gives you a setting. Going to AA from a west coast airline we had to switch to QFE for a while and what a mess that was. The 727 100 couldn't tune in the Reno altitude because of the old altimeters and the FE couldn't figure out how to calculate it so being a new captain at AA told him to leave it at QNH and do the call outs from 4400 ft field elevation and we will reset it on the ground to zero for the crew taking our aircraft so we don't look stupid. They finally joined the rest of the world and set altimeters like everybody else.