If the noise level increased as a result of the crash I suspect that it isn't because of the silencer packing. The silencer will gradually increase in noise as the packing either deteriorates or (the more likely case) becomes saturated with oil, but it is a slow gradual process and not easily noticed.
If you had a sudden change in exhaust noise then I recommend that you inspect the entire exhaust system carefully and make sure that something isn't wrong. The pipe usually attaches the cylinder by simply having springs hold it in place. If the exhaust system has been bent it is possible that the pipe isn't mating properly with the cylinder and you have a major exhaust leak. If so, this needs to be fixed ASAP
Likewise, the silencer typically slips onto the pipe. If the mounts have been compromised then the slip joint could be leaking.
Of course, if there is a big hole in the pipe that will make a big difference too!
Like arnego said, repacking the silencer is easy. Just make sure you know which end come apart!
Most of the silencers I have repacked has the outer shell disconnect from the "front", then end closes to the front of the bike. There are usually three or four screws that hold the sleeve in place. Sometimes, they use rivets to hold it together, which you have to drill out and then replace with screws when you repack. Hint: if one end is riveted and the other end has screws, it comes apart from the screw end!
When it comes apart you will have the outer sleeve, which has the actual exhaust output (and spark arrestor, if it has one) and then the part that connects to the pipe will have a perforated inner tube.
If you old packing is a big wad of gunky goo (often the case) you will need to clean the inner tube as best you can. The idea is that you want to open up as many of the perforations as you can. A putty knife is a good way to start, followed by some solvent, and eventually a wire brush.
Buy some new packing, wrap it around the inner perforated tube a few times. I use a little bit of masking tape to hold the packing in place while I slide it back into the outer sleeve.
Rod