What are dentures over implants?

The oral surgeon says it will take 4-6 months for my gums to heal. Can I still wear my lower dentures without snapping them on during this time? Does a regular dentist install the bar into my denture that will used to 'snap' onto the implants? Is this bar put onto my dentures after my gums have healed? Or can it be installed earlier, but not used until my gums are well healed? I have an ~ costs for the implants. What is the ~ cost for the bar?