You're clearly in over your head, send them to me and I'll see what I can do for you.
Seriously, though, I guarantee that there is interest in these. I am certainly interested in one, possibly more if there are different books signed. Unfortunately, value is tough to determine. I've picked up a couple through the years. One for about $65 and another for closer to $150 (my memory is shaky due to TBI, no joke) and I was happy to spend it each time. I wish I had more info for you but his signature is so rare, there is no real guide to use for pricing. Just looking at eBay, prices range from $200 and $350, up to $611. There is a letter listed for $450 and an album cover for $100,000. I have doubts that either will sell, but they are out there.
I wrote Mr. Ditko several times through the years and he always responded. I have missed seeing letters arrive with only "S.D." or "Ditko" above his New York address. He was a huge mystery to me, but I always enjoyed his art and his responses to my letters, including one about the difference between holding oneself to high standards and just being stubborn. I figured if anyone would have insight to that subject, he was the man! It wasn't a veiled attempt to get him to explain his philosophy, but rather I was seeking advice. Friends and family insisted that I was being stubborn on a particular subject but I saw it differently. My first letter was a request for a signature on my Marvel Masterworks Spider-Man volume and he politely refused, explaining that he didn't have the time for such a thing in a full page, handwritten letter that he signed. That would have been roughly the time that he signed these for you, sometime around 1992 or 1993, as Defiant was launching.
Whatever you decide, I wish you luck. Keep me in mind when it comes time to sell!