What you need is a tool called a "Basin Wrench"

You can find a basin wrench in the Plumbing section of any hardware store or home supply like lowes or home depot.

A professional basin wrench has a telescoping handle and sells for about $35 but that would be major overkill for the average homeowner....

They make a homeowner grade that usually has a red handle for about $12 to $15 and it should last a lifetime in the home.

They are very easy to use, but sort of difficult to explain in words....I would suggest you go to a real hardware store where you will get a clerk who actually knows what they are talking about and they can explain it in a minute or less.

That's it! Thanks, lazypup! I googled basin wrench and I can see how it is exactly what we need to do this. I prefer patronizing my local hardware store anyway, so I'll check there.