It would be easier to find a ready-made, in-stock window that you like at one of the big box stores, and have it installed by one of their installers.

Depending upon the building codes in your area, you may need architectural drawings for a permit to add a window. Even if architectural drawings are not required, you may find the services of an architect or engineer useful in making sure that the work does not compromise the structural integrity of your home. If neither of those are required, then yes your best bet is to find a qualified contractor who can do the work for you. Visiting a window showroom would be helpful in giving you ideas of what is possible. Have fun!