I read the reprint of Falk's article on Ojos del Salado in the recent issue of the Sierra Echo with great interest, having seen it in print before and having just returned from an attempt to climb this peak.
For the record, however, this 10-year-old account is quite out of date:
Hosteria L Murray (called the Louis Murray Lodge) has burned down, so don't try to stay there!
4WD trucks can be rented in Copiapo' for about US$110 per day. If you make a reservation from here, it's $150.
I can't imagine getting a trailer to the Tejos Refuge! It's enough of a challenge getting a Toyota 4WD there. We sunk into the sand several times and had to back up, never making it above the Andino Refuge.
Andino Refuge is at about 16700 feet, and is as far as you can drive without heroic efforts. I saw only one truck make it to Tejos Refuge at 18900 feet, and they had to let the air out of their tires and go cross-country around the sand drifts on the "road". Then they stole climbing gear from a German group and took off. Really.
It would be possible to put tents above 20000 feet, reducing the summit day from 3700 feet to 2500 feet. No one made it due to the length of the climb and high winds and cold temps (while we were there). The Tejos Refuge is a good place to stay, but not a good place to start for the peak.
The Tejos Refuge no longer has lights, solar panels, an oil heater, or a working shower. It once did, but is falling into disrepair. It's still a damn nice place for being at 19k, but not as nice as in the article. There is running water near the refuge on warm afternoons.
There are permanent ice fields that make crampons a requirement. It snows more than you might expect here (given the Atacama desert's reputation). We talked to a leader who was there in December with 1 meter of snow at the refuge. This year had more snow than usual.