I have a 2003 Sienna also.
Here is a link to a folder of pictures of projects that I have done with it.
http://rides.webshots.com/album/5765...navtype=search
One of the first things that I did was to replace the PCV valve.
It is metal, and screws into the rear valve cover.......the 2002 and earlier use the traditional press-in type, but have it in the same location.
The PCV valve location is hard to see.....I tried to show it in one of the first pictures.
Passenger side of the rear valve cover.
Also hard to get to.......easy to replace except that you need a wrench and you can only move the PCV valve a little bit with each turn due to space.
I use a slightly larger oil filter as I show in one of the pictures.
Napa Gold would be a 1516, as it is the same as WIX 51516 (NG is made by WIX).
All the dimensions are the same, except it is slightly longer (more media).
I have a subscription to AlldataDIY for my 2003 Sienna.
I also located a set of GENUINE TOYOTA repair manuals, specific to the 2003 Sienna (2 volumes) plus a GENUINE TOYOTA Electrical manual (1 volume).
I have not messed with the exterior mirrors.