$150 is about as cheap as you will get that liner in that mil shipped. Pretty good deal if that's the size you want, That's a little less than the cheapest ones shipped I found on ebay for reference.
Addy has the measurements with 6" of over lay all the way around, Which is correct. Personally I would go more on the line of 7' x 12' and give myself a 1' of over lay all the way around, the more pond liners you install the closer you can cut it, as a first install or if not certain I would give myself a little more play just in case the liner is out of center or in case you need to adjust once installed.