Oh yikes!! Well, I'm glad that I saw your original post! It sounds like they drained the transmission fluid and then put oil in the vehicle.. so you actually DIDN'T get an oil change. Might want to call that shop, tell them what happened, and get your money back. And then don't ever return.
Pull out the owner's manual and look up how much fluid needs to be in there. I will also say this.. don't just grab any old transmission fluid at Wal-Mart. Go to a Toyota or Lexus dealership and buy it there. Fluid quality matters - especially in these older vehicles.
In my 2002 RX300, the transmission filter pan is more square (my hubs calls it an allen bowl), and it's located near the middle underneath the vehicle. The oil pan is more round and has a plug in it to drain the oil.
IF yours also has the transmission filter underneath, it's worth it to just replace the filter & fluid pan in addition to adding the fluid. It's not all that expensive. I think we paid around $60 total for the parts, fluid & everything when my husband did mine.