Help with ISX 15 CM 2250

[Afftow]

I have a Cummins ISX 15 CM 2250 that is leaking a small amount of coolant into oil and burning it through exhaust as well. Under oil filler cap there is a small amount of white milky oil. You can smell the coolant on passenger side of engine as well. Appears to be going through exhaust. Coolant level is dropping slowly. Oil levels are not increasing though. Had it scanned and injector number 3 failed first part of Cummins performance test . Was told by a Cummins rep that it was probably the injector cup that was bad or the egr cooler was going bad. Took tube off that goes up to egr to check for moisture but it is dry. Took valve cover off to look for moisture and milky oil as well. No milky oil but rockers had some rust on them. Cummins has a injector cup repair kit and tool to install these parts but only can be done at Cummins dealer. Told it would run between $3800 - $4400 . I have not done a pressure test. Any suggestions on what I should look at before I dump money into a new head. Thanks