Leaky fuel injector-

I have quite a bit of gas leaking out of the #4 injector directly onto the exhaust, I was wondering if I were able to replace what looks to be an o-ring from underneath with out splitting the upper manifold or removing the injector. I have access to 2 bolts from underneath and am able to see my leak area yet I'm unsure the splitting dynamics therefore I've issued myself a stop work order to research. From glancing the threads it looks like I'm wishing. Any suggestions.. Thanks-