We have never had to move a pond that had a plastic liner, but my thoughts would be:
1. move it while the weather is warm since it will be more pliable and less likely to crack.
2. if I wanted a pond (with no cost) I'd probably move the liner and try to get some more years out of it if it wasn't a huge amount of work. But I'd cut off the sides that were above water since they'd probably be brittle, then just go with a smaller pond.
3. Or, I'd follow number 2, use the old liner as a padding at the new site and spend a little money on a cheap liner since I do love a pond. We have our first pond that has a cheap liner and a second pond I dug and installed a rubber liner. Both ponds are doing well and have for many years (2001)
4. Then I'd put some barley straw in an old nylon stocking or net bag and lay that in the pond to keep the stinkin' algae away. That has worked with my pond pretty well except if there is a rapid swing in temps. in the spring. You can see our ponds in a video I finally put together for fun on YouTube.
http://www.youtube.com/watch?v=VAh9UYqtJgo I've hesitated to show it on A4A because my weeding is not up to snuff!
5. The frogs and wildlife will find your pond, no matter where you put it. At least that has happened here.