Your dad is correct. The lids that are used for canning have a wax ring to help with sealing. Once you've used the lid, that wax is not going to reliably seal again so it's best to discard. Without a good seal you have the danger of bacteria and illness which could be severe.
It's also not wise to reuse jars like spaghetti jars because you have the danger of not sealing and also the glass could break in the boiling process and then you'd lose some of your food that you just worked so hard to can.
The best way to can is to use real canning jars that say Ball or Kerr on them. Those jars can be reused safely for years. Also use lids and rims (rims can be reused) that are branded Ball or Kerr. It's easy to get canning jars at garage sales or off of Freecycle or Craig's List if you don't want to buy new.
Buying the jars and lids/rims makes canning expensive the first time around, but reusing the jars and rims makes the whole thing cost effective very quickly. Good luck!
