STM, I think it's perfectly normal to feel worried and imagine you won't cope. I felt like that with my second child as I'd had a hard time the first time (although great drugs made it much worse for my DH than for me!). Round about full term with my second child I began to worry that I would have to be induced again (as I was with no 1) and the same traumatic time would follow. I started to think about an elective c-section, we talked it through with the consultant and he strongly advised against it but promised that I would have a c-section if it all went pear-shaped again (basically DS1 had to be pulled out with ventouse and forceps and it was all a bit dramatic). However I'm so glad I didn't, I was induced again but labour was much shorter and the birth was textbook.
I guess what I'm really trying to say is that no-one knows what their personal birth experience is going to be like. I would guess that as you're young and fit, you'll breeze through it. Yes it is painful (don't let anyone tell you otherwise) but if you choose to give birth through the front door rather than the sunroof, don't be afraid to ask for pain relief - it does work! And giving birth when it goes according to plan can be an amazingly empowering and positive experience. I was on a real high after having DS2 (and DS1 when the drugs wore off!).
Having siad that I haven't had a cs so can't compare. A friend of mine is pg with her no 2, she had to have an emergency cs with her DS after a long labour (which strikes me as the worst of both worlds!), she's a tiddler and her DP is a big bloke, chances are the baby is going to be a biggie and she wants a cs to avoid complications which she has assessed, on experience and probabilities, may occur. Good for her I say, I'd probably do the same.
They say our bodies are designed for childbirth but if I were god there's no way I'd design it so something so big has to get through such a small hole! Conclusive proof god is a man, if he were a she she'd have designed something a bit less painful!
I hope you have a great birth - don't let fear put you off, it's natural to be scared of something you haven't experienced. You're obviously getting as much info as you can which is great. To be honest the 18 years that follow birth is what you need to prepare yourself for!