Same here. But, I do know, you need to make sure that the input of the projector can read the output on your monitor. I've seen some projectors can't read resolutions over 1024x768. But, that was about 8 years ago. Need to check what hz that came show (ie. 60, 65, 70, 75, 100...), monitor resolutions, 16 bit - 32 bit resolution. Also, you may want to buy a splitter box that use on both your computer and your projector. That way, you can have the monitor running at the same time as your projector.
 
I haven't worked with projectors for some years. So, perhaps nowadays, you don't have to worry as much.
 
I've also seen places where you can build your own projector for about $300.

Yes, you'll need to check the resolutions and so on as theefool says.
 
As far as using your monitor as well, some projectors has input and output, then you can plug the monitor in as well.

Though, pending on the placement of the projector, you may need to buy a very long cable that will reach from the projector to the computer.

Thats true, but they are looking for portable projectors

Hmmm, I always thought most projectors were portable. Like those old projectors that the teacher had in the 70's.

lol, that brings back memories, and if you were the lucky one you had to go fetch it from another classroom and take it back

I just liked, as other children did during this timeframe, to make shadow figures, while the teacher wasn't looking....or was she...hmmmm

Didn't we all those were the days, being in school was still fun, well, I had fun:)