Like Tadpole said double triple layers of underlayment. With sharp rocks use underlayment under your liner and on top of you liner. You can use anything that won't breakdown. A crane around here is in the $100 per hour or slightly more range. If you have any excavating buddy's ask them if any of thier mini trackhoes can do the work. Either way your looking at a $300-$500 bill I would guess.
St.louis Ponds and Waterfalls
"We bring life to your backyard"