The truth is that most of my friends don't even think of oral sex as sex and is no good talking with them about this subject - Im really ignorant about this: what's the likelihood of getting AIDS or other diseases with oral sex?
Your friends don't think of oral sex as sex??? Hmm . . . one wonders how they would classify it. Penis Popsicle high-protein snack, perhaps? To get an answer to your question, I'd suggest you read the information in the archives. We have a whole chapter dedicated to oral sex (or high-protein snacks, if you wish). Briefly, there are different levels of risk, depending on the STD and the type of oral sex. For instance, STDs that cause sores and blisters (like syphilis and herpes) are quite easy to get from all types of oral sex (getting or giving). Common STDs, like gonorrhea, chlamydia and NGU, can be contracted from sucking and getting sucked. Hepatitis A, intestinal parasites and herpes can be quite easily passed through rimming without a barrier. It's much easier to transmit or acquire STDs when sores, blisters or discharge ("the drip") are present.
HIV is not easy to transmit or acquire via any kind of oral sex. However, there have been well-documented cases of getting HIV from sucking ("giving head"). The message here is that "low risk" does not mean "no risk!" Bleeding gums, gum disease and sores in the mouth can facilitate HIV transmission through oral sex. There have been no "well-documented" cases of getting HIV from getting sucked. There are no recorded cases of HIV transmission from rimming or getting rimmed. It is much, much, much easier to get HIV from unprotected anal sex than from oral sex.
Please feel free to share this information with your friends sometime when they are not distracted by their high-protein snacking.
Stay safe. Stay well.