If you have a window open make sure air is flowing into the house instead of out. Don't open your upstairs windows because it will create a stack effect and more subsurface air will enter, potentially increasing the concentrations.
The install is very much dependent on your house. Essentially the goal is to depressurize the subsurface and they will install a number of ports through the slab, hook it up to a blower that is either outside of your house or in the highest non-living space in the house.
It is relatively simple in many cases, but poorly designed systems can be a nightmare or if your house is very old, with multiple slabs or crawl spaces.
https://cceevents.umn.edu/radon-training-courses/required-readingThese reading can give you a better idea.
My training is in a dealing with chemical vapor intrusion, which operates under 90% of the same principals.
Things you want are a certified radon mitigator; not just an inspector. Your health department should have a list. Make sure they can explain why they chose which fan, because different blowers operate better under different conditions. If they can't explain what a pressure field extension test is DON'T hire them (essentially a test to make sure the sub-slab is depressurized relative to the basement. It should be conducted with the house generating the most pull on the subsurface).
I have heard that systems go for about 2k-3k in the Midwest, but haven't had to deal with payment myself.
Due to issues such as back drafting, risk of hitting utilities, drilling through your slab or foundation, needing a manometer, and code requirements for the system; hire somebody.
One area you could save money on is sealing subsurface connections into the house. I don't remember the best sealers, but if you ask the radon professional they should be able to guide you to what to use. Areas to seal would be utility entrances into your house, foundation cracks, getting a sump cover that is airtight but relatively easy to remove, and checking under any bathtubs in the basement that may have excessive soil exposed.
edited to add, if you have previous construction experience with homes you could do it yourself but the learning curve is steep, messing it up can make it worse, and hopefully it is only a 1 time thing