this link carries RPM's for Mandrake 10 of Gnome 2.8
the heading says 2.7, but all the files state 2.8.
Does mandrake have some sort of auto-updater that can do this for you? (never used Mandrake)
If not, just download all the files to one folder. Next, opne up that folder in a console. TYpe "su" for superuser, and provide your root password when prompted. Next, type:
this will install add the RPM files at once, with the options [U]pgrade, [v]erbose to give you details on what is happening, and [h]ashmarks to show the progression of the install.
If it is unable to complete the installation due to dependencies, the console will give you details on what you are missing. If you still need help, feel free to post back.