The Sequoia 2003 that I have does not have option for Navigation System, it is only available from 2005.
I feel very disappointed with the fact that I have no option of getting the manufacture's.
Talking to several Toyota dealers and local electronics store for the after market stuff, I felt frustrated again. Thay are not only much more expensive than the Toyota's, they also lose some major features I hate to lose on my Sequoia.
The rear seat entertainment system provides kids options of watching DVD, listening to FM without interfering my driving. It seems that I will not get those wondering features back if after market system installed.
Noticed there is a place selling OEM Toyota system with a comparable price as manufacture's and they claimed the installation is simple and original funtions should be sustained. check this link