Buying a 97-99 SClass Sedan ?

Considering buying a 97-99 S Class sedan...Have read posts and searched re-same..Realize everyone says be prepared for expensive repairs...Can someone give me some ideas of what to expect ?? Looking at cars in the 35k-65k mileage range...

Other than the ac problems that are widely discussed in the forum, what problems should one be particularly on the lookout for ? in this age and mileage range car...I am looking at 420 or possibly 320....

For example...Is it typical to have to replace water pump, alternator, starter, power sterring pump, etc at less than 100k ?? If so, what kind of cost...not at dealer, but at a reputable shop ??

Are there commonly encountered electrical problems ? ie-seat motors, switches, power window switches, etc, etc ? If so what sort of costs associated ??

At what mileage interval would you expect to require valvetrain repairs ? ie chains, adjusters, etc ?? and what is the range of cost or hours for such service ??

Are there areas of common concern specific to certain engine models, ie 320, 420 or 500 ( v or w class) or year models that I should carefully look for ??

Ive owned mostly jap lux cars in the past, and reading the forums makes me a little paranoid about cost of repairs....but there is something intoxicating about the Big Body benz.....heart says Benz...brain says Lexus...tell me my brain is wrong !!

Thanks in advance