You're near Dubois PA? Getting hard coal shouldn't be a problem. Depending on what kind of stoker boiler you get, going away for a weekend shouldn't be a problem. When I go away, I fill the hopper with coal and remove the ash pan. The ashes just drop onto the floor of the fire box. No harm done. You just have to shovel them out when you get home. Most ash pans fill up before the hopper is empty. It depends on the boiler you get. We were spending 4,000.00-5,000 on oil previously. Going to make it through this winter in about $1500.00 worth of coal. Gotta LOVE that!
Yes, a stoker boiler can be idled down. Many people burn them year round for domestic hot water. A very small fire can be maintained in summer.