You don't need to take the subway to get from Penn Station to 28th Street and 8th Avenue (which is in the Chelsea neighborhood, by the way, not in Greenwich Village or Greenwich Connecticut). Penn Station is at 34th Street between 8th and 7th Avenues. So you can just walk there.
Take the Downtown 1 train (of the 1-2-3, the red line), 1 stop, from 34th Street-Penn Station to 28th Street (at 7th Avenue).
To take the subway from LaGuardia to Penn Station, you will need to first take the Q70 bus from the airport to the Roosevelt Ave-Jackson Heights subway station. From there, you can transfer to the E train, which will take you directly to Penn Station.
To travel from LaGuardia Airport to Penn Station using the subway, you can take the M60 bus from the airport to the Astoria Blvd subway station. From there, you can transfer to the N or W train and take it to 34th Street-Herald Square station, which is near Penn Station.
Probably the best way to get there is to take the C or E train from Penn Station to the 23rd street stop or the 1 train to the 28th street stop. However, to be completely honest, you could walk from Penn Station to 208 W 23rd Street in around 10-15 minutes.
No, the AirTrain takes you to and from the subway, and the subway takes you to and from Penn Station. Take the AirTrain to the Howard Beach Station, and get the Manhattan-bound A train (of the A-C-E, the blue line) to 34th Street-Penn Station.
No, but it does stop at penn station and you can take the subway
You don't have to take the subway; it's 2 blocks. Penn Station is at 34th Street between 8th and 7th Avenues, and 520 8th Avenue is between 36th and 37th Streets.
Take the Uptown E train (of the A-C-E, the blue line) from 34th Street-Penn Station to Court Square.
To get from Penn Station to Worth Street, you can take the 1 subway line. Board the 1 train at 34th Street-Penn Station and travel downtown. Get off at the Chambers Street station, which is close to Worth Street. Alternatively, you could take the A or C train from 34th Street-Penn Station to Chambers Street for a similar route.
barcelona
Take the subway to 34th St (Manhattan). That's Penn Station. Take Amtrak.
3 uptown, transfer to S, then 6.