I don't eat post-workout. But I do usually have a protein/fat snack before. And I have an electrolyte drink after.

It is possible to do the same workout. Exercises often have modified versions for beginners.

I'd start out with a low impact workout to begin with. It's no fun to kill yourself on the first workouts and be so sore you are in misery. I used Leslie Sansone vids to begin with. Now after working out for 6 months, I'm doing Jillian Michaels 30-Day Shred on cardio days and a dumbbell routine on strength training days. YouTube has a million things to offer so that is a good place to search. Hopefully others will have more suggestions for you. Good luck.