PS: you can probably find a used Bolt with less than 35k miles near Portland for around $12k-$14k or so. Even with battery degradation (which is much less than on a Spark, maybe 5-10% after 3-4 years) you will have over 200 miles (summer) and over 150 miles (winter) of range. And it should last you for over 10 years, easily. You could use the Bolt for "medium distance" travel (?up to 350 miles, one DCFC session?), the Spark for "around town" (if you are a 2-car household), and rent a gasmobile those few times you drive 500 miles or more.
If you are only going to get $3000 for the Spark, why bother to sell it? Unless you only need one car. And you should be able to get more than $3k selling to an individual.
(An aside, I am rather disappointed at the decline of the "rent a wreck" business. I used to be able to rent a 5-year-old car for $10/day. Thank goodness there are sites like turo.com now, but it is still over $20/day. I always check for specials at the rental agencies, but ...)