My sister would like to upgrade from 10.4.11 in order to use the itunes store again and QVC. Is it still possible to upgrade to 10.5? Or would she have to jump to Lion? I'm suspicious of Lion myself.

My understanding is that 10.5 and later are Intel only.

Where would I find info about this and possibly purchase an upgrade?
Have you ever noticed how hard it is to find basic info on the Apple site?