hey am over in Brooklyn, NY about 2 miles from the verizon bridge
the only down side is no garage, which can kill you unless you want to do this day by day in parking lot or a big parking spot since its about a 8 hour project on paper. i do all of my work on the street and it add to time watching out for peopel and cars around you.
can read threw the install instruction here http://www.roughcountry.com/install/639p.pdf
a shop can do it but your going to have to be able to talk to them to make it sound like normal working replacing basic part so they don't kill you on labor. basically its new Coil springs, shocks, lower adjustable control arms, sway-bar quick disconnects, bumpstop spacers, adjustable track rod, transmission cross member spacers. can do it little by little but will take forever a lift and air tools help allot which a ship will have.
most shops will charge by hour and task. i know one guy that i use to just have install things and usually can get him to do it for $45 a end. other guys want $75-$100 a end. also will need a alignment after its done so that can add $100 to the labor bill and will wanter tires to fill in the jeep. so try asking around
am kind of surprised you jumped into 4" lift. not allot of lifted WJ around most i see have 2" lifts and a one or 2 with 3", plenty of lifted wranglers, xj, and zj.
try posting in the NY section to see if anyone can help