Hello
The Red Hat version is Nash 5.1.19.6, you can see it when the VA boots at the 2nd screen.
VMTools should are already installed, and it is unsupported to modify the image in any way, including upgrading VMWare Tools.
That said, you can shut down the VA, go to edit and set the machine type to be a 32 bit linux Red Hat 5 OS, boot back up, then mess with VM Tools.
I would take a snapshot prior to modifying things - there should be no effect to the underlying OS, but it has never been attempted.
Regards,
Chris Higgins