Is there a way I can get an idea of what the premium could be before I begin the process of buying the plan?

Yes, you can get an estimate of the premium that you will incur when buying a commercial goods carrying vehicle insurance plan by using an insurance calculator. The calculator asks you to provide certain details such as the coverage you are looking to select, the age of your vehicle, its registration number, the claims you may have made previously, and so on. Based on the details provided, the calculator will quote you an approximate premium. 

You can make modifications where possible such as in the coverage you have selected to ensure that the premium quoted is close to the budget you have in your mind.