When resurrecting our Phoenix (see thread "Smoking Hot Deal") we replaced the inner works of the Airsteam interior lights with LED bulbs from led4rv.com. We couldn't decide brite white vs the softer yellow, so got a mix, utilizing the brighter ones in the kitchen work areas. If we were to do it over again, I'd go brite white throughout, as it is a cleaner, fresher look in the 2009 interior, and offers better illumination.
I used the old fixtures, but had to clip a tiny amt. off the lead to get them to fit---maybe 1/16th of an inch, no big deal, accuracy not required. A great improvement in our trailer.