It is pretty normal for her to be sore after trying penetration. If you think about it, it's pretty logical. That area's never had anything like a penis in there before, suddenly it's gotta be stretched to accomodate one, so it makes sense to be a little sore.
So that answers that.
If she's up for receiving oral then go for it. If you can't find her clit then it's time to swallow your pride and ask her
If the roles were reversed I'm sure you'd rather have your partner ask and then have the fun begin, rather than always fumbling around!
And yes it is possible that her clit just isn't as sensitive as others' clits. Everyone's different and although the clit is generally the most sensitive part in most women, it's possible that hers just isn't too responsive to the attention you've given it so far.
Congratulations for taking it very slowly, and make sure you let her know how good she was at giving you head. If she's unsure of herself, having not been far with a guy, that'll be a huge booster for her
Ask her lots of questions, without appearing too ignorant, and let her tell and show you what feels good