Consumer Reports gave the 2001 and 2002 LS430 an excellent rating in all areas...I don't think there were any major issues with them.
Finding a car with motor mounts that have already been replaced will be difficult, if not impossible. Most people don't change them unless they have some kind of a problem. A 2001 or 2002 LS 430 will likely not need them replaced for another 10 years.
Sure, replacing them earlier than that can make a difference, but I don't think it is necessary. My 92 LS still has its original motor mounts and there are no major vibrations that would give me a reason to change them.
Now is certainly a great time to buy! I remember you describing how much of a difficult time you had finding your last LS, and ended up purchasing one from out of town. Lexus LS cars are very popular in Kansas City and there is generally a good selection of used ones for sale here. If you find one here, I would be willing to look at it in person for you.