I was a very active Crossfitter before my surgery. I worked out quite a bit but as my surgery date came closer, so did my symptoms increase with working up too much of a sweat or increase in heart rate.
After surgery, I started with walking on my tread mill within a couple of weeks. I have handrails so I just hung on to it. I obeyed the instructions of my surgeons and didn't go back to Crossfit until about 6 weeks out. Then I started out very light weights and low reps.
I am had enough energy but like lots of others, you really will need your rest the first 4-6 weeks for sure. Take that time, eat sensibly. Maybe use a calorie tracker like LiveStrong to keep you in line with what you need to eat to maintain your weight.
10 months later, I am back to working out regularly (well when work doesn't interfere with it that is). I still get dizzy spells now and then. I believe it may be scar tissue, or lack of proper nutrition before a work out. Who knows.
Good Luck!