Each Wurlitzer Spinet piano is unique and the price you can get will depend upon the condition of the instrument. A spinet and bench that is in good condition, with all mechanical parts working correctly, and minimal surface damage should sell for $350 to $400. If the instrument is in excellent condition, you could ask $550.
I found one online at JacksMusicStore. com that was being sold for $1,099. I found one on Ebay buy it now for $945. There was also one on ebay in poor condition that was going for only $100 dollars. Obviously the condition of the piano is going to make all the difference.
This is a difficult question to answer without more information. Which model is it? Is the exterior finish in good shape? Are the keys in good shape? Are there any dead keys? How old is it? Does it come with a bench? Is it in good shape internally? I suggest you consider having it professionally appraised.