Use a yard that has experience.
My mast has come down every year for the past 39 years. It is not that difficult, but it can be nerve wracking the first few times. Unstepping is easier than stepping because you don't have this 40' aluminum pole you are trying to position in a small spot.
The yard staff will appreciate all the prep you do. Disconnect all the wiring, loosen the turnbuckles, get the sails off, the halyards secured to the mast. Ideally, when the time comes it should only be necessary for the yard to remove 4 shrouds and lift the mast.
To make your job easier when the mast goes back up, unscrew the turnbuckles, do not remove the clevis pins holding the turnbuckles to the chainplates. Also get some McLube or Lanacote and lubricate the turnbuckle studs.