Since this is a load-bearing wall we had to build a header to span the new opening and jack studs to hold the header up. Here you can see the header and, on either side, jack studs.
Here is the opening with the mid-way stud removed and header/jack studs in place. Now for trim.
I decided to use 2 by 6's for the jack studs because that gave us the exact width to span the wall thickness and therefore eliminate the need for trim on the top and sides of the opening. We just needed a threshold and face trim. For the threshold I used a 1 inch thick native oak board, cut it to length, beveled each of the long sides and then cleaned it up a bit with a belt sander. Here's the result (it covered up a lot of ugly):
For face trim, Jennifer told me to get artistic and reminded me that we had stockpiled some salvaged rough-cut native hardwood boards with bark edges. Below you can see one of those boards being sized-up on the left side of the opening.
A lot more sizing, cutting, fitting, belt-sanding and I'd finished one side. Here's the threshold with the base of the face trim:
And here's the whole darn thing - these wide planks covered up a whole lot of ugly quick (we will see if Jennifer likes it when she gets home from work!):