Lisa, BIG CONGRATS on finishing your mystery novel! I look forward to reading it.
Sandra, I would agree with Lisa's advice 100% on your mystery stories. Put them together and publish them as a collection. I've seen readers (in the romance genre) grow increasingly sensitive about how much text is enough to justify selling for even 0.99 cents. Readers have grown used to getting really good stuff for only 0.99 cents because many authors nowadays are publishing full-length novels (typically the first in a series with the sequels priced higher) at 0.99 cents to generate reader interest. So readers may understandably balk at spending it on a very short story since they're growing used to getting so much more for that price.
As for the dated content, I also agree with Lisa. Publish as is. But maybe put a setting/date label on the first page to orient your readers. Something like, "December 1995, Chicago." Mysteries from the recent past can be very interesting such as Sue Grafton's books set in the pre-internet 1980s.