How to clean a quilt?  

You should be able to wash it without a problem but I would take it to a front loading machine. One it will fit better and as you pointed out less movement on it to hurt it. Yes taking it to be dry cleaned might be best but if you don't want to do that then I would go with the front loader. Most quilts are made from materiels that can go in the washer. I know I've put them in there without a problem.

I don't know if I'd chance washing it in a machine. I would maybe call around to find a reliable dry cleaners. Explain your worries to them, see if they can do it in the one hour or at least one day service. It would be risky to me to chance putting something that old and valuabale in any kind of washing machine. Wish you the best of luck in finding a good solution.

What about hand washing the item just in water to get the surface dirt out? Or maybe just adda a little washing detergent if the obvious marks don't come out.

With hand washing you'll have more control over the temperature of the water and the level of agitation as opposed to machine washing.