Does it make a diff if it is imported/exported as a .3ds?

No, that shouldn't have any impact, as far as I know.

I dont seem to remember it being vital that i put it in a specific folder...?

Again, no ... that isn't important. For convenience, you can save the prop to the Library for later use. Then you wouldn't have to deal with importing again.

Does it have to be parented to a specific part of the figure on which it is to be draped?

I'm not really sure. I've actually done sims on stuff that hasn't been parented at all, but I find it's usually best to parent the item to the figure's chest or hip, in case you have to move the figure around.

None of that will probably be of any help to you, unfortunately. Were you able to successfully clothify the original, unmodified prop?