I have one too, and my caps all tested fine with an O scope.. the hum for me started low, but not loud enough to even hear it while I was watching movies.. The hum has progressed and is louder now. I had my shop guys (work at a retailer that also does repairs) and our cost for a new digital amp was $200.
So luckily for you, if that cap is bad, it would take you about 2 minutes to swap it out and cost you less than $1. All you need is a solder iron, solder, and some solder wick. Those tools if you don't have them you can get for less than $30 for all (not buying Hako or expensive brand names).
If you still don't fell comfortable, take it to somebody, but some places have a shop inspection fee and a flat hourly rate.. I know our car audio installers solder all the time and have experience with it, so you might find someone that do it for you. Hell, post an ad on CL.. $20 to whoever can swap this 1 cap for me... only thing is, it might not be just that cap.. if its still there after the cap swap, your looking at replacing the digital amp i'm guessing, which is $200 w/out labor. And I'd guess at least a couple hours (it is embedded pretty well in there, a lot to take off to get to it).