OK I think you are confusing two things. You can get a updated Nav DVD for a 2009, it will not be the same part number as the DVD for earlier or later Prius. The electronics and screen resolution change from year to year, so you need a DVD for your year and model. Given that they cost $200, a Garmin or TomTom may be more economical.
I do not recommend stealing any part of a Prius. I also do not recommend documenting your plans to steal anything.
If you have them both why don't you go-ahead and give it a try- it's just a DVD so if it works great, if not just go back to the way it was.
What will you use in the 2011 once you have moved the DVD to the 2009? (It won't work, they are different generations, but lets assume it did?)
I use the U92 Navigation DVD in my Gen 3 Prius that was manufactured in 2009. I figure you're inquiring about a MY-2009 Prius and am providing this info, just in case it is what you mean. I don't have any experience with the Navigation system in the MY-2009 Prius.
