I have one of these stoves. It's fantastic, though there are a few idiosyncrasies to running it. More specifically (and importantly) is that the path that the exhaust follows at the top of the stove is flat. On the Magnums, this section is peaked like the roof of a house. The flyash on the Magnums falls into the stove so you can clean it out. On our stoves, it settles onto the flat part and builds up. It will build up to the point where it blocks the exhaust coming out of the stove. Then CO will leak out of the stove everywhere it can - imagine stuffing a shirt into the stovepipe and you'll get the idea. I found this out the hard way and spent 24 hours in the hospital sucking pure oxygen.
Now that I've scared the hell out of you, you just need to clean it out several times per season. I usually do so around Christmas time, in March, and at the end of the season. I cut the handle off an old canister vac so I can snake the hose all around in there. Takes about five minutes, and I don't even shut the stove the whole way down.
Does it absolutely need everything in the retro kit? My grate has been cracked for about fifteen years and I've not had a problem with it. As far as I can tell, the pusher rod assembly is pretty simple.
Do you have the manual for it? If not, I can probably scan mine.
One of the other features of the Magnum that we didn't get is the hot air take-off collar. After seeing some pictures of other users' stoves, I came up with an ugly solution:
It's Ugly, But It Works If you have any questions on your stove, need the manual, want pictures, or if I didn't explain the flat-section-flyash-kill-you part accurately, please let me know and I'll help any way I can.
Chris DVC500atlast informed me of it. So we went out to State College to get it. Thank you Chris. The stove needed a new grate and hopper, and some new gaskets, other than that the stove is in excellent condition for it's age. Today I called my local Harmon dealer and much to my surprise the stove is so old that I need a retro kit for it. 
The kit is about $600.00+ A new grate, pusher bar assembly Gaskets and a ton of more stuff. A $500.00 stove may end up costing me over $1100.00 
I need some help from some of you professionals. P.S. I may be selling my .357 and my Harmon mark III to buy parts. I hope not.
Scary, scary stuff, but the thing heats like crazy.
the stove has run fine for the past ten years. I didn't mean to scare anyone OUT of using the stove, just INTO maintaining it properly, if you see the difference. One of the reasons that I won't burn wood is because I am afraid of creosote and chimney fires. As a woodburner, you know the exact things to do to prevent them. This is the opposite side of the same coin. I, and everyone else here, am happy to lend whatever assistance I can. It's a great stove - fire it up!