Compiling to RPM setup/filesystem layout

I'm patiently waiting for the 7.1.2 RPMs to be released. Since there's no
indication when they may be ready, I'd like to try compiling PostgreSQL
myself.

Unfortunately, I can't just "compile" since I need to be able to replace my
current 7.0.3 installation, installed via RPMs. How do I go about this so I
don't mess everything up (leftover files and such, in addition to the
mandatory pg_dump) ? Also, how do I ensure that when future RPMs come out,
I can just use the RPMs and upgrade a compiled version?