Rummy, I dont think you will find anything useful in that price range.
After the lathe comes all the tooling and accessory's you will need to accomplish the things you are wanting to do.
I doubt you can tool up and supply a cue repair lathe for $300.
Tom1234 is right ... save up your coins.
First thing you need to buy is Chris hightower's book on cue making and repair.
After reading his book you will have a better understanding as to what all you will need to do what you want.
Unique's cue companion has a DVD with it to show you all the things it can do and how to set it up for each task.
Trying to find a used one is very hard and if you do find one it will be priced way above $300.
However almost all the tooling you would need should come with it.