Just have a Toyota or Lexus dealer do an inspection and run the VIN for service records, carfax, etc. Beyond that there is not much to look for. If its clean and received the required maintenance you should be set.
As for a comparison to the X3, I dont have an X3, but I do have an 07 335i and have test driven an X3 once.
The bimmer will handle better and the brake feel is going to be better, beyond that Id say the LC will beat it in every other category. As for reliability and durability there is absolutely nothing to compare.
Our 335 has had to have the fuel pump replaced, interior panels replaced due to defects in finish quality, the rear brakes squeak constantly (dealer has tried to fix it twice and still cant), the hood clamp/lock failed on one side, and almost left us stranded once due to the fact that bmws are extremely picky about fuel quality.
On the other hand, I have to two LXs, an 00 with 116k miles and an 01 with 113k miles....neither have had a single problem, both are taken offroad, long trips, short trips, towing the boat, etc......no problems at all.
German cars are way more expensive to have maintain as well
Thats my .02