Re: Red Hat RPM's
When you say 'if I download and install the newest version (using an RPM)' I pressume you mean download a program...? In which case, whether it overwrites or not depends on how the RPM file was made. Most will write over the top of any pre-existing stuff of the same name, but some are different. Let's say, for instance, that you have version 1.2.3 of program QXY installed under the dir /someplace/QXY1.2.3 and you then go and download a nice, shiny new QXY2.0.0, then it might install under /someplace/QXY2.0.0. Usually, however, any pre-existing installations of a program will be overwritten.
Building APACHE from source shouldn't be a problem. So long as you follow instructions so that everything can find everything else, you should be ok.