it will take about 15 hours from doha to Mecca (with short brakes for refueling and snacks and with reasonable speed of 120 - 130 KM/h)
in Mecca it is a bit difficult to find parking (especially now in Ramadan) but there are many parking areas outside the holy city and from there u can easily catch the local bus which will drop u near the gate of the haram
if u r going in this week let me know by PM, maybe we can arrange to move 2 cars together.