We've been in our house ('49 vintage) for 10 years. Putting a damper in was one of the first things I did. I believe it originally had a cast iron damper that'd rusted away. The main thing you need is a cap if you don't already have one to keep the rain out. If that's the case, I'd lean toward a chimney top damper. I put in a Chimalator, and a quick check of prices shows they've escalated to $200+ for the kit from the ~$100 I paid for ours. Price depends on the size. Honestly, I think the pricing you got is a bit steep for either type of damper, unless you have a massive fireplace and flue and a roof so steep that it'll be a giant pain to get to the top of the chimney. For the chimney top one, they're going to go up on the roof and put the cap/damper in place with screws and some RTV silicone as a gasket. They'll drop the stainless wire that is used to close the damper down the flue. At the fireplace, they'll drill holes in the masonry for the bracket to screw into the wall. Then they'll attach the wire from above and set up the tension so that the damper is closed all the way when the lever is all the way down. That's maybe a 90 minute job for someone who knows what they're doing. Marking up the material by 2X to install may be pretty normal. It's also why I DIY most things.

If you want to keep the option to use the fireplace later then you can just remove the damper. They're usually held together with a cotter pin to the damper handle. But, fireplaces have big flues. If you try to put a 4.5 inch pipe into a 12x12 chimney you are asking for trouble. You'll want to re-line the chimney and then put a metal block-off plate either over the stove or at the damper.

Due to Carbon Monoxide Poisoning Hazard Here is a link that might be useful: Dura-Vent Recall

Hey Dormelles, thanks for response. I ended up going with a Locktop damper for the basement fireplace that has the completely rusted out damper, I had read some reviews about that stylle being almost impossible to open in climates that have lots of snow, but we never used the basement fireplace as it needs it's firebox rebuilt some too. For the upstairs fireplace we went with a Chimalator but quickly discovered that our flue doesn't protrude out of the crown quite far enough so we need to still purchase a "flue extension" yet but that sucks as that's another $100 so if anyone sees this and knows of a cheaper an option I would be so appreciative. Another thing I don't love about the Chimalator is that the handle mechanism is rather bulky and kind of an eye sore in my opinion.