Linus wrote:
house is about 30 years old with soffit vent screens in need of
replacement.
They are imbedded in a cement-wiremesh and am wondering if it is
possible to just cut off the screens, clean, vacuum&blow away any
obstructions and install a new screen by just somehow attaching the
new screen in some type of frame that could be screwed into the vent
opening?
in other words, if I cut away the screen in the overhang portion of
the roof, is there a replacement vent&screen that can be retrofitted
from the outside or is this a job that can only be done from inside
of the attic?

Outside. You can't possibly reach the soffits (overhang) from the attic.

I used the 6" wide aluminum gutter guard material from HD. Cheap, easy to
work with. Using 1/4 by 1.5" lathe, I built frames for the gutter-guard
material, stapled the mesh to the frames, and mounted the frames over the
exiting holes with screws. Paint first.

I did it this way because our original soffit vents were, like, six feet
long. I also put in dozens of commercial vents (each about one foot long).
You can't have too many soffit vents.