Radio Replacement

I have a 2005 Sienna S (althoughnever heard of anyone else having an 'S', that's what it says). I have the stock AM/FM/Cass/Single CD radio. I'd like to install a later year OEM radio that plays MP3s and has an auxillary input. Can this be a 'plug and play' operation, or will I have to modify the harness?

I installed a GROM USB2 unit on my 2003.
The 2005 is a 2nd generation Sienna and much different from my 1st generation.
However, I think they make one for your Sienna.
It is a plug and play unit.....has a USB2 port that I have a flash drive in, and it has a audio IN for MP3 player or other device and it has a IPOD input.
The USB2 port has my music on it......each folder on the flash drive looks like a CD "DISK" (up to 6 folders for a single disk radio) and each song in a folder looks like a "track"....up to 99 songs in each folder.......within the storage capacity of the USB flashdrive.
So, in theory you could have 99 songs per folder X 6 folders.
Steering wheel controls still work and you can select different songs using the steering wheel controls
Do a Google search on GROM USB and I recommend buying it directly from the GROM website so that you can get technical support (free) from them.....they will ask for your order number when you contact them.

I have pictures of this unit and the installation in the "Sienna" pictures in the pictures that the link in my signature takes you to.
Remember, the pictures are showing this on my 2003 (1st generation) Sienna, but the GROM box will look the same (different wire harness).