In a word “YES” but its not going to be the easiest of jobs. To start with you need to go back to the original firm that you purchased it from and then give them the option to quote for the work. This is for a number of reasons, they will have your original drawings and will be aware of any system upgrades from the profile company that you have decided to have an upgrade from.
I would say however in most cases it is far easier to take the orignal one down and start again. The complexities of joining two sparate roofs and making sure that everything matches and looks fresh and clean will be a tall order for most companies. If you are going to consider having an upgrade on your original conservatory the cheaper option may be to keep any existing walls that you require and take down the measurements of any door apertures that are present.