When mine stopped reading discs (from kids jamming things in there like 2 games at once) I ended up buying a replacement disc drive for it. Got it from Amazon for $25-30. That is likely cheaper than the cost of a harddrive.
It was really easy to swap it out following some intructions online. Took about 15 minutes and my Wii has been working great since.
Nintendo repair costs around $100...you can buy a used Wii cheaper than that (also if your wii is modded they will refuse to repair and send it back to you)
If your drive is not working you won't be able to rip your games and would have to have someone else rip them for you or find pirated copies to download. But USB loading would work fine even with a broken drive.