Riggers usually do rigging, the wires and cables above deck on a boat.
Rudders are plain old boatyard work. Usually a plain old mechanic does the job. Either you pay the yard to hoist you in the air while they drop the rudder, then you park the boat on jackstands while repairing things, and hoist again to refit, Or you find a yard that will let you dig a pit under your rudder, and you simply park the boat, dig a pit, drop out the rudder, and start work.
Either way you need to look for hull damage and damage to the rudder tube, not just the bearings. And probable damage to the rudder, because even a hairline crack can let in enough water to lead to total failure down the line. You may very well need a total rudder replacement or rebuild, as well as work to the rudder tube and hull, unless it was a very soft grounding and the rudder just pushed down into the bottom. If the shaft was bent, it probably would not turn smoothly. If it turns smoothly, it should still be inspected very closely but the odds are it isn't bent.
Unless the rudder moves freely and normally--odds are there's more repairing needed than you might think.