Normally if they are doing a professional install (Where they send the tech out) they send the modem out with the tech rather than in the mail due to delays... so if they had sent it out in the mail I would make sure they didn't set it up as a Self Install.
If it is set up as a Self Install, and you have a cable internet/foxtel point already in the house then you should be able to plug the modem in and follow the prompts to set it up without a visit.
If it is set up as a Self Install, and you have a cable internet/foxtel point already in the house then you should be able to plug the modem in and follow the prompts to set it up without a visit.