PinkCloud : It's true, one of the "fun" experiences of being newly pre-op is figuring out where everything is and what's going on down there.

Both the "slight erection" sensation and the muscle one take some experimentation to recognize, much less control; if you do try clenching on the dilator a few times, you may get a better sense of what's going on.
And, yes, the farting!! I get little bubbles trapped in my labia, which is gross and could NEVER have happened before (my wife says it's normal, but I had to ask her half-panicking the first time!). Also, you *can* actually get a little air trapped in the vagina, especially during dilation; it's harmless and it's not actually a fart, but it'll feel a little bit like it when it escapes.
I still sometimes have a tiny drop or two of pee trapped somewhere in there when I'm finished wiping, too, that only reappears when I stand up. I do not miss having a penis, but it was certainly more... straightforward, and sometimes cleaner.