Congratulations - fantastic news!
Twins are brilliant (I'm only saying this now as mine are asleep! Ask me again at 5pm...).
Totally agree with the above bit about having no choice.
My DH and I had 'failure is not an option' as our motto in the early weeks.
You will be fine.
A (twin mum) friend told me when I first found it that, 'you are only lucky enough to get twins if they already know you will cope'.
I wouldn't necessarily get two of everything straightaway. We bought too much really. We never bothered with moses baskets, and had them in one cot until they were 5mo.
See how you feel about finishing work early. I worked until 34 weeks - but we had builders in so work was preferable to home...
The best thing we did was for my DH to work really hard during my pregnancy and then manage to persuade his work to let him take 6 weeks off. I don't know how I would have coped if he had gone back at two weeks.
I had an ELCS - got the impression the midwives were a bit disappointed. I was very scared of giving birth and DH was absolutely terrified something would go wrong. Stick to what you want though, most places let you choose. Because you have a DD already, they may encourage you to go for a vaginal birth, but do what you want to do.
Also, we researched a pram v carefully and got the Obaby zoom tandem (second hand but still £500), but actually only really used it for 8 months (and I resented it a lot of that time..!) It was great to get them into a maclaren twin triumph and be able to get on buses / tubes a bit more. Definitely glad we didn't buy it new!
The only thing we have bought new was the carseats / mattresses & cots. Everything else of ebay / charity shops. I haven't worked it out, but I think we have saved a fair amount.
Oh, and be ready for people saying 'Any time now!' etc. when you are about 25 weeks!
Take care and good luck!