Hey Chuck,
For the plug to show fouling after only 50 miles it has a significant oiling source so this should be easy to isolate. You said you are not a serious gear head so the tools needed for these tests are cheap and easy to find if you do not have them already. A vac gauge is maybe 10 bucks and very useful tool and compression gauge is a rent-able tool but a good one is only maybe 30 bucks but maybe not a tool you will use often. Get 1 that stays at max pressure reading until cleared by user. Cheaper ones must be watched as they return to zero without pressure applied. PS... Remove coil wire during test for a couple of reasons. Do a vac check next as this will tell many things. Record vac. @ an idle (10 to 20 inches depending on cam etc. is expected) and then at say 2500 rpm but give it about 30 seconds at this steady rpm before recording reading (same or near idle reading expected). Now look at
idle vac again. Look at needle condition not reading = is it steady or is needle vibrating at a swing of maybe 5 -10 inches on gauge? Is there any sign of
oil in coolant (check cold engine to be safe) I am leaning hard to either a manifold gasket around head port or the bolt length that can break into port runner. Good on 0077 for his post as a possible. Look at hose end from the PCV valve as it attachés to intake or system to see if it enters near or where
oil could be dumping
oil into the affected cyl. = I think this is a stretch as it is fouling plug so fast but agree they can suck oil and create problems. A leak down test is best way to isolate issue but at this point and fouling speed a simple compression test will show good or bad hole. Please let us know what ya find?