I have a white first-gen Wii that will no longer read discs. Said Wii was used at least once weekly for a long time before...

Try looking in the SD card slot to see if there's like a piece of plastic or something like that stuck in there, and if there is, you can try to remove it with a toothpick/dental pick/whatever pokey thing fits in that slot. If there's nothing in the SD card slot, you might have to replace the SD card reader.

If you have an electronics shop near you, you could remove and bring the dials from the machine and look for similar ones at an electronics shop. If you don't have an electronics shop near you, you could order some from Amazon or a similar site. However, you will need a schematic to make sure you buy dials with the right impedance OR you can check with a multimeter.

You could try to clean the SD card slot by putting isopropyl alcohol (IPA) on a SD card and then putting it in the SD card slot, taking the SD card out, and repeating the process for 3-5 minutes. (With the Wii off.) The IPA will not harm the electronics as it is very fast drying. Hope this helps!!