I still would have the injectors serviced while you have it all apart. They are going to get clogged sooner or later. Even if the engine runs well, it could still benefit from cleaned injectors. Yes there are two o-rings per injector. One at the top that seats in the fuel rail and another at the bottom that seats in the lower intake manifold. If that one is so badly cracked that it leaks, you really need to replace all 12 of them. when you have the one leaking injector out, carefully examine the top of it. As for removing the injector itself, it can be a PITA if the o-rings are old and hard. Alot of twisting and perpendicular movement will be required. If you pull up at too much of an angle, you risk the pintle cap, and spacer getting lost in that intake valve cavity. I have all mine out, sent them out for servicing and should receive them back tomorrow. On one injector, I did loose the pintle cap, however, I retrieved it out with a pick. When I receive them, i will post a picture of them.