Don't jump to conclusions just yet. The usual suspect is the intake camshaft sprocket. The chain tensioner and the chain itself are very robust, I wouldn't worry about those failing. For now, let's assume the sprocket is bad (it probably would make a sound coming from right in front, seeing as the magnet may pick up some noise and make it sound like its coming from the very front). Replacing it is not a dramatically huge deal, remove the valve cover, take the chain off the intake sprocket, replace with a new sprocket and work your way backwards. There is one kink in the operation, your chain MIGHT not have a master link, which could make it annoying to remove. Before reinstalling the chain though, you MUST remove the chain tensioner and reset it. You car does have an automatic chain tensioner, however, it's a little bit different due to how chains stretch over time. Think of it as a "ratcheting" mechanism. Once it clicks forward one notch, it won't go back on its own. What's going to happen is: you will remove the chain from sprocket, so obviously, there will be a lot of slack in the chain, so the tensioner will try to eat all of it up (it's spring loaded), and will go to full tension. Unless your engine has a million KM on it, the chain will not need to be in full tension. If you install the chain like that, when you turn the engine over, there will be so much bending force on the intake camshaft that it will snap at the sprocket end. If you've ever seen those threads like "oh no, my intake camshaft has snapped and wrecked my engine, what do I do?" I promise you the reason it happened is because the person did not reset the tensioner. Resetting it takes about 30 seconds, you remove it, you open it up, you put it back together, pushing the internal pin 1 click only, if you felt 2 clicks you are already too far, and you put it back in.
Anyway, assuming the tensioner is bad, or the chain is too stretched (an outcome which would be really surprising), it still isn't a terrible bother. Zip-tie a new chain to the old one, rotate the crank until you've got the new chain all the way through, reset the tensioner (or replace it with a new one), and if you aced it you won't even need to adjust the timing.
M104/M111 engines are just a joy to work with.