It sounds like your garlic is ready to be harvested! Congratulations!
Yellow foliage is a good sign. A thick stem is a sign of a healthy plant. So pull them up, gently (you don't want to break the stem off). If you have to go rooting around for the garlic heads, be gentle and use your hands. A tool might cut into the heads.
Save a few cloves for planting this fall (or next spring) and mark the area so you don't dig up the developing heads in spring, before the new plants show themselves above ground.
As for peas and tomatoes, there is too much to say here. You can find advice for these plants here on Almanac.com.