With the serp belt removed, you will have easy access to the upper and lower shock bolts.
I changed my serp belt about 6 months ago and didn't have any problems at all. If you know how to take the fan off, that's half the battle. On the tensioner, loosen the big (19mm I belive) bolt about 2 turns before turning the adjusting rod (13mm). When you go to refit the belt it might seem like the new belt is too small. The tensioner pully has to be pushed over by hand to get the new belt on. That one of the tricks I discovered on my own.
About dropping the upper shock bolt: I did the exact same thing when I was adding a rubber washer to fix a vibration problem. The nut went down into the pully area. It took about two hours using a flashlight and mirror and magnet to fish the nut out. Fortunately I got it before it did any damage.