Whatever seal it is, try this before spending any serious $$$ to fix it. Switch to a High Mileage conventional engine oil, like NAPA sells. Valvoline makes all NAPA branded oils.
High Mileage engine oils have restorative additives added that can restore seals so they no longer leak. Especially if it currently has synthetic engine oil in it which seems to more commonly cause such seal problems more than conventionals do. My daily driver BMW lived on synthetic and it developed a major rear-main seal leak and was leaving a real mess on my garage floor every day. After getting a nearly $2k quote to fix it, a BMW forum thread suggested I switch to a High Mileage conventional and damned if it didn't fix it after maybe a week of driving. I wasn't a fan of synthetic engine oils even then but the records said it had gotten nothing but synthetic Castrol before I bought it so I stayed with it... I was really happy changing to the High Mileage conventional fixed that leak!