Questions about 1994 E420

[screedchan]

I recently purchased a 1994 E420 with just under 100,000 miles. Although I had the car inspected by a reputable service facility prior to purchase, it continues to have a persistent oil leak. There were also two other leaks involving one of the transmission cooling lines and the power steering resevoir. On Monday, I plan to have the mechanic put the UV dye in the oil to see if that shows where the leak is coming from. It leaks about one tablespoon of oil from the time I park at night and the next morning. I went with the E420 over one of the six cylinder models since I had heard that they were less prone to oil leaks, particularly at the head gasket. Nonetheless, I had also heard that most German cars, including Mercedes, are prone to some oil seepage/leaks. I don't really understand why Honda can build a $15,000 car that probably won't leak oil for at least 150,000 miles, but the German cars obviously have their advantages as well. Is there a particular gasket which has proven to be troublesome in the 4.2 liter engine? Also, as part of the purchase, I had the front rotors and pads replaced, and they continue to emit a nasty squeal some 1200 miles later. For some reason, the mechanic does not like to use the sticky compound on the back of the pads, but I seem to have used this product on other cars without a problem. Is there something about the product which is detrimental to the E420? I plan on insisting that he at least try using it to see if the squeal goes away. Thanks in advance for any replies.