I forgot to try to answer your questions about prices.. There is a very wide variation because of new vs. used and instalation differences.
A new VF3000 or Kaa2 are around $4500-5500, pipeing, valves and a circulator pump, maybe anoter $300-500. A chimney will vary greatly.. I prefer a masonry chimney,, I put up my own, It wasn't difficult,, just work.. I borrowed scaffolding, and used my tractor front-end loader. The height will determine material costs.. Stainless steel chimneys are less labor intesive,, but are not 'forever',, a masonry chimney will last a century or more. SS about 15-25 years,, depends on climate and maintenance.
A new stoker stove will be at least $1500, up to $3000+,, I prefer LeisureLine stoves,, I like the electronic coal-trol stoker/thermostaiic controller. But all the stoker stoves available are very good, Keystoker, Harman, Leisurline, Alaska etc..
If you shop around you should be able to save about half on the actual coal burning appliance.. I bought my stoker boiler off of Ebay, and with the help of forum members got it extracted from it's former home and I came and got it, rebuilt it, and used it last season,, for about 1/3-1/2 the cost of new.
If you find a larger stoker boiler locally,, you could add heat to your basement, or do underfloor radiant, and even add heat to the garage,,, if you have excess capacity.
Hope this helps... Greg L