In my Galaxy S3 16, I have two SD cards. The larger is the internal memory and the smaller is RAM I think. So does this mean I can change both? One (the larger) from 16 to 32 and the smaller from 2 to whatever?
No you don't have two sd cards. You have internal memmory that is built in that can not be changed, if you bought the 16gbmodelmyou are stuck with that. You have 2gb of ram(random acces memmory I believe) and its built in and can not be changed. It's used for short term memmory for use so you processor can store stuff there while running the many functions it needs to operate. The only things that be changed out are your sim card and you single sd card that can handle up to a 64 gb micro sd card. That's all you can do.
I have the 16 gb phone, and I popped in a 32gb MicroSDHC card. totalling 48gb I keep all music and movies I rip to MP4 with handbrake on the MicroSD card. everything else I leave on the phones internal memory.
Once in a while I copy off old photos and videos to free up space, I shoot a lot of pics and vids and sometimes end up with only 1gb free on the phone.
Still loving my GS3, I'm loving the Samsung commercials making fun of those iTools waiting in line.