I've made several transitions (upwards and downwards)- pistons>4 eng heavies>bigger heavies>HS748 twin turboprops>shorthaul twins>really big heavies.
In each case, none of my anxieties materialised. You very rapidly transition to the new scene. So what is involved? Enjoying it- it's the most tremendous fun! You will find you adapt very very quickly- just bump up your speed as required.