welcome aboard, Looks good from all I see and have read so far, sounds like you have been doing a lot of pre-reading, I like hearing that! Going to be a really nice pond!
1st question i have to ask, what kind of fish are you planning on keeping? this can make a huge difference on what you may want to use for filter. Liner, use a underlayment, I don't care if it's a commercial grade, sand and carpet padding, old carpet, just use someting, You'll be glad you did. go with 45 mil EPDM liner. More flexible, last longer, virtually puncture proof, far better liner than PVC, Not the cheapest but in the long run a good liner for the money. Skimmer and Pump, So many options, explore the options and pro's and cons. My advice, go with proven brands of produccts over cheap inexpensive ones. This doesn't mean they are the most expensive this means they work and last. IMO, I would rather pay twice the price and fix it half as much. LOL You'll get some good advice here, just take the time to make sure what you choose fits what you want to accomplish in the pond. In other words, don't build a goldfish pond and expect to keep a bunch of full grown Koi. There is a difference in fish load and basic needs.