A few drops of oil under the filter? Just where under the filter? On the engine side? At the top, or was it at the bottom? It might make a difference, and waist on the right side while facing the front of the car, what weight of oil did you use, was it a good filter or a bad one? Are you sure you got the right filter, was there any smell of gas? Did you put a new pcv valve on? That's very important when DIY, and did you use a good one, don't use one that comes in an orange box as some of them are known to be bad but not all are bad just some, you will have to visouly check them out. Be sure to chech where the hose connects to the valve as that might be important,but maybe not,just maybe if they used a good hose, some did,but you never know. How loose did you leave the drain plug, remember you will need to take it off to drain the oil the next time, be sure you don't get the plug for the atomic tranissionas you may have a mess on your hands and then you have to get the good bolts to refasted the pan to the transmission,some bolts are not as good as others. It's best to get bolts from AMCE bolt company in Hoboken, NJ, but you must speak to the right salesman to get correct bolts, I believe his name is Sam.
Back to the few drops of oil, how often does it drop? One drop every 30-35seconds or more often,if so how often, and what is a few, 2or 3or more than that, Ifs it's more like 5 or 6 every so often,it could be a problem,but then it just be a slight leag which could be normal. Did you use a new crush washer on the plug or is it the filter that's leaking? The filter seat may be defective, if so you may need to pull the engine and have the filter seat resurfaced, this is a simple procedure once the engine is out. It's helpful to hane a few extra hands to do this and be sure not to drop the engine. Oh yes and get ahold of Sam for new bolts, I'm sure he can get you the right ones,, be sure they have the right markings in the ends, those are the ones you will need.
Hope this helps.