It might be a good idea to set it up in advance, and make the trip to the Lexus dealer for an extended test drive. You'll probably find A LOT of differences, both good and not so good (maybe) between your 2002 and the 2015. Different engine, transmission, driving characteristics, new technology and amenities. Almost too many to summarize here. The reliability will most likely be there but a lot has changed in the 13 years.
As you indicated, $49k is probably a stretch for a 335i or a C400. The 328i and C Class with the 2.0t are probably doable.