Hannah was posterior and felt contractions in my back. She turned during (7 hour) labour and came out fine.
Mason was anterior but turned 90% posterior during (75 minute) labour. He got stuck, but with some gas, a bit of fancy leg and hip positioning and LOTS of bracing against the two midwives' hips he came out in 13 minutes of pushing.
My midwife said if he was my first then we'd definitely have needed some extra help (forceps/ventouse, possibly a c-section) but given things had already been stretched out previously he was sweet to get out.
I didn't tear, but Mason did nick an artery inside the vaginal wall on his way out which needed a stitch.
So I think you'll be just fine