Fuel Injection - explain this to me like I am 6 years old

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I am now getting 12.5 mpg on my 71 Duster 318 4bbl. It literally runs fantastic, finally. So what cam is in it? What gears? what Stall?

I have been thinking about installing electronic fuel injection. Price is an issue for my wife at this point in time. Would like to keep it at $1,000 or less.Not much available for that

Does this sound do-able and would it be worth it? Probably not an probably not.
Would it dramatically help my mpg? That depends on why your carb is so far off
What advantages is Fuel Injection. After the tune is in; driveability, fuel economy, engine life, lower maintenance

I know very little about it and have not really started to educate myself on it. I know that on my other cars there are injectors for each cylinder, and the after-market seem to use one injector in place of the carb.

If it makes sense to do, I will at that point learn what I need to know.
As others have said.