Might be time to change the frets...

It's been 3 years now and a few months ago the 5th fret on the G started sounding very...broken (for lack of a better term).
Every other fret on every other string gave off a tone, this made some sort of screeching sound no matter what I did. It can be heard in my Aces High cover, during the fast scale-like fills.

Yesterday, I noticed the same thing with the 10th fret on the same string and I'm pretty sure it wasn't there earlier.

Does this mean I have to change my frets? Is that even possible? How is it done? Asking how much it costs it pointless because of the price difference, but how about a relative to, say, a pack of solid quality strings. Is it a lot more or around the same?

You know this has crossed my mind recently as well. All of mine are getting flat on the top, but it still sounds okay. My seventh fret is bad, but only on the D string.

Obviously this would have to be performed by a professional. If I do anything like this, I think I'm just gonna get a new neck.

You could do it yourself but i suggest taking it to a good luthier. They will find out what the problem is and can fix it (if it's not the frets).
Just out of curiosity what bass and strings do you have/use and how old is the bass?

I said it's 3 years old, it's my first bass and I've put around 3 hours a day on avrage (sometimes none, sometimes 6) of play time.

The strings were changed multiple times, but I only used these two:
Warwick Red 40-130
D'addario Pro Steels, same gauge

The bass is an Ibanez GSR205

Sorry completely missed the 3 year bit
You have played it quite a bit so it could be fret wear, using the steel strings (as I think the steel would 'eat' into the frets more than the nickels but i could be wrong) wouldn't help much either.
Worthwhile taking to a luthier or some form of guitar tech just to get it checked out, could be something completely different.\
I just tried to find the fret wire on the ibanez parts store (just to get you the part cost) but couldn't find any for your bass.
You may only need a few frets replaced (if the frets are the issue) so it may not be too expensive.

Thanx man!