Widening Basement Door

Not sure if this is a basement or masonry question, but here goes:

My house is a block and stucco rancher with a full, walkout basement. The door is a standard exterior one, maybe 32 inches wide. I want to remove it and widen the opening to install a sliding glass door or maybe French doors. I plan (unless otherwise advised) to use one of those metal lintel bar things, but I'm puzzled about just how to put it in place. Is it necessary to somehow support the wall before widening the opening? If so, how? I thought of maybe using my circular saw with a masonry blade to remove the mortar between the courses of block where the bar would go, inserting it, then cutting the opening wider below it. Would that work, or is it just crazy? Is this something the average DIYer should even attempt? I've worked with brick and block before but nothing like this.

 

hi
the top part must be supported before you cut out the door opening
used screw type jack post and place some 2x10 to make a beam and place them between the jack and the joists.
then cut out and insert metal lintel between the floor and the cement block
fill in the gap with cement block and cement to secure it to the wall

 

Excellent. Thank you.