Can I still work out my abs if I have a hernia?

That depends . The type of hernia can dictate what you can do. There are many patients with hernias who work out on a regular basis with no problem. If you have symptoms, however, you should see a doctor asap.
Depends on size. If the hernia is inguinal or abdominal, any workout will make it grow in size and could worsen it, even causing incarceration and pain. You should have it repaired before you continue any abdominal workout regimen.
Probably. In order to answer this question, i would need to know the location/type of hernia, it's size, your health (and size), and your symptoms. In general, if it is small and not affected by exercise, you are probably ok, although it may lead to the hernia getting larger. Your safest bet is to see a hernia surgeon and ask them their opinion--words cannot replace a careful physical exam. Good luck!