Welcome, Gary! I'm glad you're able to play again.
I took a few decades off and returned to guitar about 5 years ago. I suck much less this time around!

From what I've seen your old 1956 Gretsch Synchromatic might run between $2000 and $5000, depending on condition and exact model. A few rare mid-50's Duo Jets, Silver Jets, and Chet Atkins can go between $8000 and $16,000. (sorry)