It looks like from the second pic you want to change the roof. So that's a building contractor to change it. If it's tied into the main roof, and how it's tied in can be a factor. That would be a seperate cost from the new roofing. How much it can cost can depend to an extent on where you are, what kind of roofing you want. It also looks like the siding is changed between the first and second pic, not sure if you mean to change the siding or just the color there.

Zero return on investment to reframe that roof from a gable to a hip, could even be seen as a detriment as the gable prevents water from getting in the steps.

IMO, the hip porch roof looks a lot better. Not a lot of square feet so there won't be all that much runoff from the roof.

I assume that this would be part of a re-roofing project?