I just wanted to add a quick note of thanks for this wonderful guide! I went with the suggested free Vera Serif font and it's great. No it did revolutionize my 505, but it's just that much more comfortable to read. Plus in doing this I used the PRS Customizer which (without me even thinking about it!) gave me the clock in the bottom right and I love that, too.
Thanks!
p.s. - now if only we could get an official firmware update that would build in some options for changing the default fonts.