Do I need autofocus with 50mm lens?

I want to buy a 50mm lens but my camera(Nikon D3100) doesn't have a build-in focus motors, so I need to buy a 50mm AF-S that has the motor inside.
The difference in price is big( around $300+) so my question is:
Do I really need 50mm with AF-S?

If you want autofocus, yes.

Manual focus is not a big deal. Just needs some patience and practice. Since you have got on to the DSLR band wagon, don't shy away from manual focusing.

No you do not NEED it.AF is a convenience - there's nothing wrong with manual focusing (its what we used to do all the time with film cameras).

I'm going to go cautiously with the other answers.

The big concern is that you may find it difficult to precisely focus your Nikon. Because most people get and use AF, the fine focus viewfinders are an accessory, if available at all. I see magnifiers but in a very quick search I did not see replacement focus screens for your camera.

Macro-work often needs manual focus and landscapes with a 50mm should have little need for auto-focus, it will be those moderate range shots at low-f# that might give you a little trouble without AF.

That's the problem with these nice cameras, they see better than we do!

Depends if you like to photograph things that move.ie: people vs buildings. With candid, sports and live action auto focus is really helpful, especially if it is dark with a flash. With still life, nature and architectural photography where you spend ten minutes setting up a shot on a tripod, its no big deal to focus, plus you like the extra control and would turn off the auto focus any way.

I have a Sony A300 and I too bought a 50mm macro lens.
My camera has the AF option, but I always always always use MF. I personally think after practice it became so much quicker. Where the 50mm is so precise, it takes a while to focus on certain things depending on your surroundings, etc.
If you're familiar and comfortable with MF, then I'd recommend getting it.