More RAM won't affect load times - the hard drive speed is what affects that. More RAM simply allows you to have more programs/files open at once. For example, when editing large image or audio files, the program might be able to load the files into RAM; or in games, they can load more levels into RAM at the start, to avoid hard drive accesses during gameplay.
But to answer the question, some testing utilities:
Memtest86+ - boot disk utility to fully test RAM for errors
Everest - check memory amounts, and the Serial Presence Detect info - the RAM's own ID information.