No need to touch the outside yet. I wanted to post a photo of a wall on a 100 year old house.
Everything seemed fine, and did not matter because we were adding a addition and this wall was going away. DIY does not like the format of the photo, here is a link to it.
Could you imagine trying to install a exterior door in that wall?
We want to assume your house is built exactly as it should be, As a remodel carpenter, I smile when I see things were done right, so many surprises when you open a wall.
Couple weeks ago I opened a wall and installed 2 french doors side by side, 4 doors.
I new there was a electrical wire to deal with, was an outlet under the existing window.
Open the wall and find the home run to the service panel was in that wall.
This was a simple fix, but added time and money to the job.
Just remove the drywall and plaster from the inside, and the whole story will be out on the table. You will see what obstacles you need to climb over, be it electrical, plumbing, bad framing. Is all easily fixed.
My only point I am trying to make, what looks like a simple job may be simple and smile.
You are willing to get your hands dirty and jump in and work.
First step is expose the framing and let us see what you are working with.
Is no contractor you can hire with x ray vision to know what is in the wall.
Said contractor will charge you by the hour, on the remodel, or hit you high on a bid to cover any surprises he may find.
By removing the drywall yourself, you are removing the surprise factor. And saving several hours on labour for demo. But nobody here can see inside your walls either.