Welcome to the garage.
The (5-45RFE) tranny pan is sealed from the factory with RTV and to me this is the best option. I did use a prefab gasket before, but it started leaking over time. RTV gives more work (especially at the next fluid change when you have to remove it), but it seals better.
JEEP Grand Cherokee 4.7 Lmtd 2004
HID 8000K in low and fog / Quad Squad member
KYB Gas-a-Just shocks / Pirelli Scorpion ATR 245/65/17 - Transgo reprogramming shiftkit.