I'll answer these in order.
1. The paparazzi show up in public places like clubs and parks. If they see you and you have a high celeb level then they will take pictures of you. If you don't have a gate around your house then they will show up there to take pics.
2. No, you don't read about your sim in the newspaper, but if you gossip with someone else, you may hear about other people in your family.
3. If your sim is involved in a scandal then their celeb level does not go down. They get an embarrassed moodlet for 3 days unless they sue for slander at city hall. Also, other sims won't want to hang out with you for about a week.
4. To become famous, you have to socialize with celebs. It's best to start by talking to level 1 celebs because they are more easily impressed by you. Then work your way up to higher level celebs. You get A LOT of points for kissing/marrying/dating/becoming best friends with other celebs, even if they have a low celeb level. Also, if your parents are celebs, when you are a kid you start with a higher celeb level, up to level three.
-Jenny
Yes you can, you can find pre-made celebrity Sims on Mod the Sims and Sims Exchange, just search for whichever celebrity you want and follow the instructions on how to download it into your game.
You can be have a limo and you can be a rock star but no you cannot be a celebrity without late night.
get a music job but also practice your guitar
As it so happens yes. Hence SIMS 3 EXPANSION pack. Install it exactly how you installed sims 3.
That happens in sims 1 and in sims 3 for iPod touch Mabel other sims too
You can get a LIMO by being a mayor or by having 4 to 5 stars as a celebrity.
You need to have sims 3 late night and you have to befriend a celebrity if you hover over them and they have a star next to their name you've found a celeb to impress!
They die
Nraas has a mod called "Master Controller" that now allows for the deletion of all celebrity stars. Search google for his wikispace.
They get taken away
no, there aren't any aliens in the sims 3 like there are in the sims 2
you get it on Late Night expansion pack