Nice lunch place near LIRR
If you want something like a Korean diner with unaccountably classy decor for its price, go to Han Bat on 35 between 5th and 6th and get Hyaemul Dolsot Bibimbap (mixed seafood bibimbap in a hot stone bowl). Not much else will be that good to get there (jigaes and such will be oversalted), but the place is definitely convivial, and you can have as much banchan (complimentary side dishes) as you want. They also make barley tea; ask for it, it's pleasant.
By the LIRR, you mean Penn Station?
The Breslin - only on a weekday, though, weekends are pretty busy
John Dory Oyster Bar
Eataly - only on a weekday, though, weekends are pretty busy
Koreatown options like Madangui, Don Bogam
Co. aka Company
El Quinto Pino
Trestle on Tenth