I inspected the view from the web of the CVS
and noticed that the file problemRandomize.pl is in the HEAD distribution but not yet officially in the rel-2-4-dev distribution.
You can get the file using
cvs update -A problemRandomize.plwhich will get the very latest version of problemRandomize.pl
In general I have found it fairly safe to update pg further (i.e. to a later revision) than I update webwork2. The macros and lib files don't require reconfiguration and (usually) don't require the installation of new CPAN modules so the updates are fairly easy.
For your second question:
Updating will not change any settings in your local installation -- this is why global.conf.dist is updated but global.conf is NOT -- you must transfer any changes in global.conf.dist to global.conf by hand, modifying them to conform to your local settings and configuration. Updates that involve updating the configuration files or adding new CPAN modules take a bit longer and are more work than other upgrades.