First thing I would do is bring in an engineer to determine if you risk the wall collapsing by doing this, as from here I don't believe anyone would feel comfortable answering this question.

+1

I would have an engineer or a very capable contractor look at the project.

It can certainly be done, it is just a question of what sort of re-structuring you will need to do.

There is no significant structural loading under a window.

The loads have already been transferred to each side of the opening (or the opening would have already collapsed).

there you go, you have the brickeyee seal of approval to change your opening without risk of your house collapsing!

I don't think the question was whether or not a window was load bearing, but rather what would need to be done to re-structure the opening.

It will require the installation of either a new header beam or some sort of steel lentil to support the weight and load of the structure above it.

That is correct. I was thinking, as is normally the case, that we are removing upper courses of brick and going up.

If nothing changes at the top end (width or height) they are fine.

"there you go, you have the brickeyee seal of approval to change your opening without risk of your house collapsing!"

"The rough opening is wide enough however the height is too short. I will need to remove the exterior cement window sill and 2 full layers of brick below it. "

Reading the OP and understanding how loads are transferred around openings is not all that hard.