How much oil should my Six be leaking?

Hello,

Hate to start a new thread since there're already several others on the topic of leaking Slants, but I figure, eh, whatever.

I've just bought a '71 Plymouth Scamp, not only my first classic but my first car generally. It's got a 225 Slant Six that's largely original, from what I understand, but runs well.

I know a little about cars, but not how much oil a Six like this should be leaking. I've heard that it's normal for these things to leak some oil, but how big of a stain should they be leaving behind?

I took two readings off the dipstick, engine cold, and it'd gone from the "Add" line the day after I bought it to below the "dd"s in "Add" the next day.

If I brought it into a garage like Mr. Lube or Canadian Tire, would they be able to discern much about what's leaking without removing the K-member?

Also, judging by the location of the stains under the car, it may be leaking a bit of tranny fluid, I think. Is that also normal?

Sorry if these are stupid questions, but like I said, I'm sort of a :newb:.

Thanks for any help.