Doors and Windows - replacing exisitng door and frame

Hi, I would like to know the steps to replace an old door with a new one. The exisitng door has been damaged in the bottom by water penetration, as well as the jambs. Plese indicate to me what is needed to replace the door and the frame. Ex: type of caulking, best type of wood, etc.
The door is a main access door, embedded in a brick face front, and please tell me what to put in the new door to prevent water penetration.

I want to take this to a contractor, but I want to understand the process of it first to know what the work entitles.

Thank you very much for your help.

Welcome to the forums! In your situation it would be best to purchase and install a complete framed door unit, remove your old door and frame and install the new one. 99% of the time, you don't have problems with fit, as they are all made alike. Be sure to order one with brick mold on the exterior. This will slip beside your brick and require minimal adjustment and caulking.
As far as a choice of doors, my favorite is fiberglas, while others may prefer metal or even exotic woods such as mahogany.