Holson, I recommend that you get a PPI done by an experienced MB tech. The overheating seems to be the aux fans not running, but why? Just because the owner has the original window sticker, brochures and papers doesn't mean that the car was maintained properly. Does the Maintenance Booklet show that this car was serviced regularly? The condition of the brake fluid suggests otherwise unless an indie installed something other than MB brake fluid, e.g. ATE Super Blue Racing brake fluid. If not done already this car is due for a new voltage regulator. The deteriorated hood pad, cracked interior wood and cracked driver's seat left bolster are normal for a 15 year old car. Does it appear that the leather was ever conditioned? Leatherique could do wonders for the seats if they're not too far gone.
I have two 300CE's and the proper oversize tires are 205/60 R15 ... with the 65 profile the speedometer accuracy may be affected slightly - no big deal, but worth noting.
The Kelley Blue Book Values for this car in our area is $3,600 - fair condition and $4,600 - excellent condition. Of course, condition is very subjective and the desirability of the car may make it more valuable. As you probably realize there is a limited number of 300CE's in the USA, let alone ones for sale. Go to
www.kbb.com and check the value for yourself based on your evaluation of the condition.