Dealer is a ripoff. Find a local shop that sells at least near retail price and is familiar with the N54. They will need the proper tools to replace the injector seals, since the injectors must be pulled to remove the cover.
You also have to drain some of the coolant to replace the filter housing gaskets. Also a good idea to change the oil, too.
E92 335i/6MT Dinan Stage 3: intercooler, oil cooler, intake, flash, exhaust, LW dual-mass flywheel.
Vishnu PWM methanol custom trunk mount, Diffsonline 3-clutch Salisbury custom diff, Ohlins Road and Track coilovers, Vorshlag camber plates, much more...
E28 M5 w/ buncha stuff, R171 SLK350