Hi Ben you have an ADT powemax by the sounds of it.
It will need some parameters re programming as you guessed and this can be done by any competent company. If you post your general location someone on here may be able to assist further.
The system will have an engineers code unique to ADT but this can also be defaulted/changed.
The devices are also unique to ADT so if you wanted to add later then your options are limited to second hand or ADT
My suggestion would be to get a local, reputable and recommended company to have a look, I'd also advise you have it under some sort of maintenance agreement, this could save you in the long run.
Finally you may also have a dummy external bell, so this is worth checking too.