I bought it recently and stashed it away in the garage since the thing weighs more than my son.

This is my first scope, I bought it a good price, IMO. What would be a good price to sell this for?

From my limited experience, I believe it's working properly, however, I could be wrong.

 

Varies a lot, and from location to location. Just from your limited description I'd put it between $50-$100, but less may be a good answer too.

I have an old HP120B scope I need to get rid of. I'm pretty sure you can still get most of the tubes.

 

You should probably keep it, analog scopes are good for some things that digital ones aren't.