have you seen the stove in person?
i think that will have a lot to do with the real answer in this.
$800 is not a bad price DEPENDING on the condition. the enamel paint on these stoves can look god awful if it hasn't been cared for and is now chipped up (pretty much irreversible damage). more importantly, at $800 the internals should be in good working condition short of possibly needing a new catalytic combustor which may be an acceptable investment if all else is good. this means the metal internal components should not be warped and the refractory should be ok. refer to the following diagram:
http://www.discountstove.com/2190.html
parts 27, 28, 35, and 36 should all be in good condition.
digging deeper, you will want to make sure the refractory assembly #9 that holds the combustor is not crumbling and falling apart. it alone costs $210. then there is the combustor itself which should not be crumbling and that is $200 to replace.
fully evaluating all of this is the difference between the stove being worth $800 or $200 honestly. if all of this isn't up to spec then the stove isn't going to run properly.
unfortunately there is no way of seeing the refractory & combustor without pulling 27 & 28. 27 comes right off (if not warped) and 28 comes out by popping the two wedges (21) that hold it in place. stove should be vacuumed out well before doing this.
i believe my 2190 was made in the early 90's and it is actually holding up quite well. i paid $300 for it a couple years ago (a rare deal but they are out there). i bought it without inspecting everything first due to the price. worked out though. refractory was in fair but operable condition. on mine, i can move 28 just enough to remove and inspect the combustor but i need to remove 35 or 36 to fully remove 28 and see the refractory. i'm guessing due to some very minor warping.
this stove has been around long enough that there are enough parts to be found. can your local dealer who would need to order it call and get it easily? maybe, maybe not. but if you order online or call/email enough dealers you will find what you need.
so you see why there is a love/hate relationship with this model. its not simple. all that considered, to me its one of the greatest stoves out there in operation and efficiency!