$300? I'd have done it for coffee!

Firstly, I confirmed I had a problem. My 80mm and 43mm lenses both
stopped at infinity before I left, and I had to think about that because
the 150mm is a new lens (to me) and heard it focuses a "bit" beyond
infinity.

I pulled out the little plastic plug to the right of the viewfinder.
Inside are two screws. The one farther in (on the top) is the vertical
adjustment. Don't mess with it unless it's off. The raised screw is the
rangefinder. Put a lens that you know stops at infinity on the camera
and haul it over to it's farthest distance. Point the camera at a
distant object (antennas on the top of the "Fuji" billboard on the
entrance to Columbo Mall closest to Benifica stadium worked for me),
distant like a mile is good. adjust the raised screw a bit and look
through the viewfinder at what you did. Once the images are as perfect
as you can make 'em, turn the lens back and forth and check again.
Remove the lens and put it on again, and check. It should be rock solid.

I was surprised mine went out of focus. It's ridden in a motorcycle tank
bag for hundreds of miles and it never lost adjustment.

10 minutes to do the adjustment. 15 if you take your time.

Good luck!

JD