Yes this i9s the same as a rear main seal, which is short for a rear crankshaft seal. The rear always refers to the end of the motor connected to the transmission.
I am not clear on your email. Are you in the final stage of an Auto-Rx treatment on your daughters RX330? Or on your RX300?
In the case of the RX330, the first thing I would do is have the PCV valve, sometimes called a CCV valve inspected or replaced. This is part of the crankcase breathing system. It is designed to allow the motor to expel internal pressure. Internal pressure is created by air and unburned fuel that slips past the piston rings during operation. This is called blow by. Piston rings are not a perfect 100% sealing device. All motors have blow by some more than others. If the breather valve is sticky or stuck closed then the internal cavity of the motor builds positive pressure. This forces oil out at the weakest point. A poorly performing PCV valve also leads to sludge formation and oil consumption. The good news is that it is a pretty cheap part.
In solving a rotary oil seal leak with Auto-Rx it is important to use conventional motor oil and not full synthetic motor oils. Conventional motor oils have a mineral oil base. This tends to stiffen the seal material a bit, as opposed to synthetics that tend to keep them very pliable.
Rear main seals typically weap or leak from a build up of oil contamination that builds up on the end of the steel crankshaft, right where the polymer rear main seal interacts. So some junk gets caught up at the sealing lip. The shaft is no longer perfectly round as it is spinning.
By allowing Auto-Rx to clean the crankshaft and seal material, it has a good chance of finding its old polymer memory and perform once again. I cant stress enough how important it is to run a mineral oil based motor oil, to enable the polymer seal find its orginal shape and stiffness.
It is a very labor intensive proposition to change out the rear main oil seal. The transmission has to come out etc.
