Transmission Leaks

I have a couple of small leaks in the transmission, one in the cooler line and another where it goes into the side of the transmission case. My question is: will pouring in a bottle of transmission leak-stopper do any
good? And if so, what is the best kind to get?
Not directly related to this, but what is the best viscosity of oil to use for a 91 300CE? I know nothing about oil and don't have an owner's manual yet.
Thanks!
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Don't be intimidated into fixing every little oil stain on a 12 year old car. They're not significant, will not cause a massive failure or even oil consumption. Leave them and DON'T put additives into the transmission.
As to what oil to use in the engine see: http://api-ep.api.org/filelibrary/Guidechart2002.pdf
and change the engine oil and filter every 7,500 miles or 5,000 miles if that makes you more comfortable. Change transmission oil and filter every 30,000 or 35,000 miles.
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Just add transmission fluid as necessary and be careful not to overfill. Your leaks aren't that bad but you can always tighten the screws on the transmission pan if you feel compelled. As for oil, 5W30 is great for cold weather (below 30F) and 10W40 is good for summer. If you have dino oil change it every 3500 miles, synthetic every 7500.

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Thanks for the tip. I don't know what type of oil is currently in the car. Is it safe to just put in 10W40 to top it off or do I need to flush out the old stuff and start anew?

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Add 10 -40 if the existing oil is still relatively clean.
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