Why would you need to see if the printer is ready?
Opening the printer this way (the only way to really print the way you want on a dot matrix printer) doesn't mean that windows whon't put the job in the printer queue...
So, if the printer isn't ready, the job will stay in the printer as long as the printer isnt't ready...

You could check the EnumJobs API func.
The EnumJobs function retrieves information about a specified set of print jobs for a specified printer