Should I care about SPF??

As long as you are 30 or greater. You definitely don't want to be spending any large amount of time outdoors w/out some level of protection. It's bad for your skin's appearance and texture. But more importantly it can lead to skin cancers. Skin cancer can usually be treated if caught early, so if you haven't been wearing any sunscreen, or you've been tanning (don't) then you definitely need to keep an eye on any moles you have to make sure they aren't changing, and if they are you should contact a dermatologist.

Yes! If you don't you will regret it.

yes definitely! putting a good sun protectant on will only benefit you. it will protect you against skin cancer and could reduce the appearance of sun spots and rinkles.