It's really not that hard. While I don't actually live in Manhattan, I'm not very far.
You can hit the farmer's market at Union Square and other places, there are several vendors there that sell grassfed beef and tons of veggies/fruit/etc. Barring that, you can order over the web. I like Northstar Bison myself, though there's US Wellnessmeats and other places.
For general stuff, I buy from Costco, then, anything that's not available there, I hit the local supermarket for.
Workouts: I have a bunch of dumbbells in various sizes. They don't take up too much room because I hide them under an ottoman that sits infront of one of the couches in the living room. I work out while listening to metal. I also have an exercise bike in the basement, but I use this at the highest resistance setting and only for a short time (~30mins-~40mins).
I fast walk about 20 minutes to/from the train station and work. You can make a game of going around the tourists, news stands, fire hydrants, flier/free news/ads boxes, etc, or piss off the bikers by walking in their lanes (jk). Sometimes I find it a lot more expedient to walk next to the sidewalk than on it due to the high concentration of slow walkers.
Also, there are others like me that like to race, so make an effort to walk faster than the other guy without breaking into a run. Some get pissed off, others also love the challenge as I do. :)
At lunch, I fast walk through Central Park, so it's about a total of an hour of walking a day, more on the weekends. This also provides a good bit of sun exposure.
I cook my meals on the weekends, and pack them in the morning, bring them in glass pyrex containers, use a metal fork/spoon and stainless steel thermos. I avoid using plastic (well the pyrex container has a plastic lid, but I don't heat it), and avoid the probably BPA lined coffee/water paper cups at the work by using my thermos. Snacks are jerky, nuts, berries, also packed.
Going out drinking, I usually just have either red wine, or tequila with a side of soda water (aka seltzer, but the bar dudes seem to prefer soda-water as a name), or whiskey.
Except for too much wine, drinking this way, I never get a hang over. I do eat some bar food, for example buffalo wings, but you can also order things like a Caesar salad and avoid the croutons/dressing. If they have sweet potato fries, I do order those, even though sometimes they have a flour coating - I don't get much of a reaction to the small amount.
Avoid things like mayo and ketchup as the mayo's from industrial oils, likely soy, and the ketchup's made with HFCS, but the ketchup in very small amounts isn't that terrible - the mayo's far worse.
Grilled shrimp if they have it, or a shrimp cocktail's great too.
Going out for food, sashimi works best, or a lean steak, or maybe a seafood soup without noodles. Obviously if the group is going to a sandwich, pasta, or pizza place, you're not going to participate.