As what justin911 state... you have 3 months to re-register you car before it gets de-registered. From that point, all you need to have your vehicle registered is to have a RWC. You dont need to book an inspection time with vicroads as you were the previous owner at time of the vehicle being de-registered and also the current owner at the time of having the vehicle registered. Basically turn up at any vicroads when your ready ... show them the RWC, pay your rego fee and its all done...