I have never modified the focus of my lens, so cannot report any experience into this.

Technically, infinity is not in focus until f8, according to the Widelux DOF charts. I almost always shoot at f8 or f11 and at least 1/125 sec (better would be 1/250 sec.) in order to maximise depth of field and ensure a sharp picture. You may need to switch to a higher speed film to compensate for shooting at smaller apertures and higher speeds.

I haven't heard of people reporting problems with infinity in focus; usually modifications are made to have the lens focus closer than 8 feet by shimming the film rails so the film lies a few mm further back from the lens.

This page discusses readjusting the focus of the lens if you really want to try:

http://jumboprawn.net/jesse/cams/widelux_ro.html