Vansco Treemont catalytic stove, should we buy? How to operate?

We looked at a stove from our local Craigslist today. See previous thread:
https://www.hearth.com/talk/threads/cl-stove-id.105305/

It is newer than I thought, dated 1990, and is a catalytic stove. Now we've never had a catalytic stove and I know very little about them. We need a larger stove than our current one, an Earth Stove model 1900. It's been a decent stove, we've heated with it for about 10 years. (purchased new)

This Vansco seems to be in good shape. The people that own it know nothing about it. It's very dirty inside, they've been burning trash in it, and I mean literally, trash, saw an eggshell and whatnot inside. So I expect to replace the Catalytic Combustor for sure. Have looked around and seems to be around $150 to replace.

Can somebody tell me how this stove is likely to operate? I can't find a manual for it anywhere. There is a small lever marked H and L on the left upper of the stove. Also a pull out lever on the right upper, I'm guessing this is the bypass damper?

So I guess what I'm asking is there likely to be any major issues with it and would you buy it if you were looking? ;-) And how to operate it if we do buy it?

Some new pics below, their house is very dark:

I've done some searching and most things I find are others looking for a manual as well. I did find a copy on ebay for the fireplace insert model, and that should be close enough for operation directions. Still pondering....

Looked at a lot of manuals and read up on cat stoves. Think we are going for it! We are going to give them $100 tomorrow and they are going to hold it for us until our tax refund comes in. So I'll probably be back in a couple of weeks with many questions. ;-) Our area has a pitiful selection of used stoves, this is the only one I've seen on craigslist worth taking the time to look at. We are getting it for $500 which seems like a decent price, even figuring in a new cat for it.

Firebox is 22" front to back, 24" side to side and about 14" tall. For comparing, our current Earth Stove's firebox is 15x17x14. Our house is currently only about 900 sq. ft. but 10ft. ceilings, slab floor, and an under-insulated attic. We are planning on adding about 750 more sq. ft. to the house as well as a 14x16 sunroom, hopefully starting this summer. We will also be adding more attic insulation this year. The earth stove is ok most of the time but when it gets really cold it's hard to keep up. We have a few electric heaters for backup but rarely use them.

Thanks! I will be sure to report back. My husband said he will have to learn how to cut wood again. He's used to cutting it 16" for the Earth Stove, and this one will take a lot longer pieces!