How would I know if I'm getting an OEM quality slave cylinder?
OEM quality doesn't have to be a necessity.
With the 4cyl, you have the AX5 trani.
If you have the external salve, just make sure it is a NEW cylinder.
If you have the internal slave, it needs to have the tubes already installed.
Don't use the ones that need the tubes installed.
A couple of important things to know about...because this is your first clutch.
Removing the pilot bushing/bearing will be difficult if you dont' have the right tool.
If you can rent or buy the tool, I highly suggest spending the money.
Some say the grease trick can get it right out.
I have never had it work for me on any of the 27 clutches I have replaced (27 is a close exaggeration).
If you dont' have a torque wrench, go get one.
The clutch will never be right if you don't torque the bolts correctly.
Once you get it all back together, make sure you bleed the clutch cylinder correctly - don't bleed it like you would brakes - bleed it without releasing built up pressure - open the bleeder valve before the pedal is pressed down and close it before the pedal is released- no need to 'pump up' pressure for the clutch - check the fluid bowl every other pedal stroke so it doesn't go empty.
Most important - keep plenty of comsumable fluids at your disposal.