[78F350]

Call the shop and ask them about the codes, or hopefully you can read it on your receipt.
Buy a simple code reader. If you have a smart phone with Bluetooth, you can get an ELM327 device that plugs into your car's OBD port and can link to an app on your phone (under $20 on Amazon, eBay, etc.). Otherwise your local parts store should have a selection available or they may offer to read/clear your codes for free. The most common codes would be related to Secondary Air Injection system faults and O2 sensors. Not a big worry if it is those.

I had a similar leak on one of my 99s with 128k miles. I was sure it was the RMS seeping. I didn't worry about it for a long time, but it slowly got worse. I took it to a good local independent and had them fix everything 'while they were in there'. Nearly $4,000 later I had new mounts, front crankshaft seal, RMS, IMS, transmission service etc. They found that the RMS was actually fine and the leak was from the IMS bearing seal. The IMS bearing was still good, but I had them install a new LN ceramic.
Normally I do all my own maintenance and have done all those jobs on other cars. In this case it was well worth the money to me due to time-stress and peace of mind knowing a skilled pro had done it all.