We recently got a new server box (RHEL 6.4, running as a Virtual Machine) in at our office, intending to use it primarily as a database replication source. However, our tech set up the partitions so that there are only 50 Gigs of free space on the root partition, and the database software (PostgreSQL 8.4) that our hardware guy pre-installed on the system is set up to put the data files in a subdirectory of /var/lib/. (This appears to be the generic default location for PostgreSQL to install into.) Given that a single copy of our database currently tips the scales at ~ 8.8 gigs, that we were intending to set up three copies on this machine for the replication process, and that we do expect our database to grow, I'm foreseeing a not-to-distant future where this setup ends up running us out of disk space on the machine.

The machine in question is set up with a /home/ partition showing ~164 gigs left. I know it's possible to swap the install from one directory to another if you're compiling the code yourself, as I've had to do that several times before now on other systems. I'm kind of hoping, however, that there's some way to get YUM, which appears to be the package manager installed on he system, to let me set it up in another location on-disk (in the /home/ directory, of course) without having to recompile.

Is this possible, or should I go ahead and start downloading the install pack from the PostgreSQL website now?

I would expect that PG would have a config file that tells it where the files are (other DBS do). It probably just defaults to that location.
I really would not expect to have to re-install.