I feel your pain... at in 2008 i had very similar surgery... My L5/S1 is pretty much dead and the one below that (the very bottom one) is severely damaged.
I was 24 years old so they said they wouldnt do a disc replacement on me as they said it only lasts about 10 years, so they did something called a 'Wallis Ligament Procedure' where they insert a piece of artificial ligament on one side of my spine, which is then tightened to ease the pressure on my discs.
I also went private, and was in hospital for 4 nights, and also did the fainting thing when trying to walk
However - the absolute most important thing that you have got to do is GO TO PHYSIO! I didnt, as i wasnt referred, and basically had no post-op support. As a result my back got progressively worse as the muscle they cut through became so weak, and in my first 2 years following the surgery, my disc continued to slip and i was off my feet for lengthy periods frequently. I could stand up for only 30mins at a time, and couldnt walk anywhere far.
Sadly for me however, i would deem my surgery a failure as the pain still affects me on an almost daily basis. I am unable to do any physical exercise with the exception of cycling, which really depresses me. I used to play sunday league footy, basketball, and also boxed (so i was doing exercise 6 nights a week) but i now cant do any of this, and have since put on 5-stone
So - good luck to you, take it easy, enjoy your time off work, but please go to physio!!!!