There is zero chance that you will have to do this yourself or ask for special services. I traveled with my arm in a cast and with it in a sling. If you ask politely, anyone around you will help you, FA, Other travelers, etc.

dont worry about about it for one second!!

but I will add that travel In economy (you are not) is really uncomfortable with broken arm/arm in cast/sling. I would not wish that on anyone and paid for upgrade to business personally....