As someone who had a dentist phobia as recently as 4 months ago, I can help you be a bit more at ease.
As Sandy said, definitely talk to your dentist regarding your fears. If your dentist is good, he/she has been through this before with other patients, and will be able to help you through your fears.
I had 22 teeth pulled in April, and was given immediate full upper and lower partial dentures right afterwards. The nurse first gave me some nitrous oxide, which really helped me to relax, and then the anestethia (sp?) was given to me. I feel asleep, and before I knew it, the process was over. If you are getting 18 teeth pulled, are you having an oral surgeon do it? It may be worth going that route.
As far as foods I was able to eat - soft foods work best. I ate lots of mac/cheese, cooked pasta, and stuff like that. At first, you will find it VERY weird to try to eat with the new dentures. Heck, ask the others on this board. They dealt with a few panicky questions from me a few months ago. After time, you will feel more comfortable eating your normal foods as you adjust to eating with the new dentures.
I never really got "sick" after all the extractions. I just felt woozy from all the painkillers I had to take for the next 4 days as I recovered from my surgery.
Facing your fear is the first most important step. No one really enjoys going to see the dentist, however you can work with your dentist to make your stay as comfortable as possible. Keep in mind, that any temporary discomfort you go through during your extractions, will be worth it!!! It certainly was for me. I have a wonderful smile now, and it really makes a difference!!!
Please don't hesitate to ask any questions about dentures. We can all try to help.