Info on Xmark triggers...
http://www.remington.com/sitecore/content/Remington/pages/xmark-pro-trigger.aspx
It is user adjustable without taking the rifle apart.
However, it states that this version came available in 2009.
Earlier versions are not, and I believe it stipulates in Remington documentation that these should only be adjusted by the factory.
IMHO, any trigger that is not specifically designated "user adjustable" should only be tuned by a qualified gunsmith.
F'rinstance...
Years ago I allowed someone who, while not a gunsmith but who seemed, and claimed, to know his stuff, tune the trigger on my Rem. 700.
That season, upon returning to the truck after a hunt, I flipped off the safety...and the rifle discharged! As always I had the rifle pointed in a safe direction. But let me tell you, there are damn few things that will scare the unowhat out of you more than that!!!
I immediately took the gun to a REAL gunsmith. It was so screwed up, including by liberal application of Lock Tite, that he had to scrap it, and replace it with a Timney.
I later learned that this kind of occurrence with Remington triggers is not terribly unusual.
I've also read on another forum of similar experiences with the earlier Xmark trigger after being played with by untrained hands.
Again, IMHO, it is just not worth the $25 or whatever bucks saved to have a professional gunsmith,
who knows what he's doing, to take on the potentially enormous liabilities, both financially (think lawyers) and physically/emotionally, that could result.