It doesn't seem that much effort to me - you don't need to reinstall aolserver or posgresql to start with 4.6 instead (if you are using the required versions), just checkout the oacs-4-6 to the place where you currently have unpacked the 4.5 tarball (backup before if you modified something there).
Anyway, your current error looks like a configuration issue again. Check the 'library' parameter:
ns_section "ns/server/${servername}/tcl"
ns_param library "/web/${servername}/tcl"
Did you look for an example nsd config file that is referenced from the OpenACS documentation? This stuff should be mentioned in there.
