[Yosemite Sam]

It really depends on what is wrong, there are any number of things it could be.

Not to worry about sounding stupid, I sound that way all the time and it doesn't bother me a bit.

Everyone can't know everything about everything, if you've never messed with something like this how would you know???

You don't mention anything about grinding the gears, when it doesn't want to go in gear does it grind?

I guess the first real thing to check for is, when this happens, check to see if the drive shaft is still spinning (along with the engine) when you push the pedal down.

When this happens, what do you do to get past the problem?

I think the answers to these questions can give us a better idea of what we're looking at.