I got this Wii about 4 years ago, and it had worked fine until now. When I put the disc in, it won't read it. A message along the lines of "An error has occurred. Press the eject button, remove the Game Disc, and turn the power off" Sometimes It will let me enter the game, but I am never able to play before the message pops up. I have tried cleaning it, by using compressed air to clean the dust out, but it doesn't help. I would like to avoid sending it in, but if it has to be done... Any suggestions to fixing it?

That compressed air thing never works.I have had the same problem and I know How I can help you.
#1.Try unpugging your wii for several minutes.
#2.If your game is a dual layered disc (SSBB,Metroid Prime Trilogy,Metroid other M)Then the dust your wii may have gathered over the years may be the cuase of the problem.You can get a wii lens cleaning kit at Gamestop for 10 dollars.This usually does the trick.
#3.Inspect disc for any kind of damage.
#4.For further assistance here is nintendos consumer service number
1 800 255 3700.
Hope I helped.

you should try getting a disc cleaning kit i am preety sure they sell it at walmart