Hi there firstly congrats on meeting your bub so soon!
I had a c/s 8 weeks ago so will give you my answers.

* how painful is it? i didnt find the op painful at all - the recovery is slow and long and I agree - you need to take it easy as possible so you can recover quickly
* What pain relief is given? I was given quite a few different pain killers in the first 2 days which was good as i was up and about the next day without having to worry about being in too much pain. At home i just took pnadol when needed.
* how will having a c-section affect my ability to breastfeed? i was lucky enough to have baby, DH and a midwife with me in recovery and i had skin to skin contact and breast fed in the first hour after her birth - ask you carers if this is possible! Also be prepared for your milk to possibly be a little slower to come in - mine took 5 days, others take 2 - its best to be ready for it!
lWill my ability to have more than two children be affected? nope! it shouldnt unless you have some other complication or pre-exisiting condition
What are the odds of being able to have a vaginal birth for the next baby? Very possible hun - lots of info out there about vbac's and obs that support it - I want a water birth for 2#!!

HtH and the best bit is because you cant do housework etc. you have so much time to bond and spend time with your little one! Thats the upside I guess and i think its well worth it!! Good luck!