Rusty, as you can read in another string on this forum, I had the factory do the bracing on my '07 Alante in June, 2007. If memory serves, they would have started doing this mod. in early 2007 and continued up until their demise in the spring of '08. But, as I noted, they only installed TWO such X-braces, while current mods seem to call for 3, along with some diagonal lacings along the floor of the basement. As a structural engineer, I actually consider the TWO bracings to be counter-productive and will be doing more such work soon as I get back from this trip. So, YES, if you buy this coach you should have supplemental bracing done and if they tell you it's been done, be sure you have at least THREE X-braces in place.
But this is a great coach, so don't let this be a detriment to your purchasing it.