Kyle,
this might be just like that old adage that advice not requested is often not appreciated.
but in for a penny...
I wouldn't worry about market value at that level; more concerned over total cost to make it a reliable runner.
I mean, what can you buy used for three grand anyway? Something else with high miles...
only you know what else has been replaced on it. If trans, shocks, muffler, cooling and front end have been rebuilt, maybe investing more in the engine is a good idea.
I ran into this a number of times when I did family financial planning. Usually one spouse wanted to get rid of a car when the other one
wanted to fix it up. Not having a car payment and paying cash for repairs so that you remain debt free is a real motivator.
One might always ask oneself, is it better to buy a used Toyota or Honda? If one is reinvesting in a daily runner for a longer commute that gets 20 mpg, then alternatively choosing a 40mpg diesel Cruze or VW Golf or any number of affordable hybrids for longer commutes would justify the cost in order to lower overall cost of operation.
but then of course you get down to the bottom line which has to include whether you like the car, whether you need a full size car,
or is it time to sell it for salvage. An eleven year old Impala ought to go 300K miles if maintained. Particularly a small block V8. Assuming the Impala had the V6 that was the Buick clone, it was supposed to be a very durable motor also. So if you rebuild them, they should last a long time.
Or donate it for a possible tax credit. I hope this helps somehow so you consider all the alternatives.
now back to regular programming.