Can I install the Homebrew Channel without an SD card?

I would like to install the Homebrew Channel on my Wii in order to play DVDs. Since I don't have an SD card, I was wondering if I could install it using a USB. I have a Version 4.2e system.

No, you cannot.

Okay. If I bought an SD card, could I download whatever is needed onto the SD card using the wii's internet connection? Obviously, I don't currently have the hardware to interface my PC with an SD card.

No. You need to connect to a computer somehow. If you can borrow a camera or something which takes an SD card, that'll do the job.