This is a very tricky situation. If you do not provide proof of interlock installation, your bond will be held insufficient (i.e. a warrant will be issued.) On the other hand, selling your car could result in you being ordered to wear a SCRAM device on your ankle. SCRAM is very expensive.Call my office if you would like more information.
You are in violation of your bond if you do not put the device on your car in a timely manner. Your bond can be revoked and you can be put in jail. If you sell your car, then the judge will probably require a SCRAM device which is just as expensive. You need to hire a good lawyer to help you address the issue of finances with the court. (And my guess is that you either are not a first offender, you blew high on the breath test, or you were involved in an accident - any of which will cause you to need a good lawyer.)