DO IT!
I bought an LMT two stage trigger and the hammer pin kept coming out. I called LMT and talked to Ryan who said the hammer must be missing the J spring. We got into a bit of an argument, he insisting it must have been omitted at LMT and I insisting I must have dislodged it. We agreed to disagree. They replaced the hammer.
My basic LMT upper runs great. Only thing I ever had to do was replace an extractor spring.