Some of your questions depend on your total gallons, such as pump and filter size. For a pump recommendation, you can't do better than Pondmaster for durability and longevity, and they come in many different sizes to suit the size of your pond. Many of Pondmaster's pumps are made in the U.S. too, another plus in my opinion.

I have no experience with small ponds, so I can't answer the filter and pump size questions, but since you live in Dallas, the fish you mentioned, feeder goldies and mosquito fish, should be fine outdoors, since i doubt that you will have a prolonged freeze in your area. Comets and shubunkins are another choice. The exception might be the fancy goldies you mentioned putting in later. They are more delicate and may need to spend the harshest part of the winter in an aquarium if you have periods of extreme cold.

In your area also, you will probably want to leave the filter and pumps running all winter, since I don't expect that your water would ever completely freeze.

For plants to leave outdoors all winter, most plants are hardy in your zone, zone 8. For suggestions, blue pickerel is an excellent choice, dwarf cattails, water pennywort, arums, cardinal flower, aquatic callas, and depending on the size of your pond, you might have room for some dwarf lilies.

Heres a link that shows various plants including a picture and describing their zone requirements.

Happy ponding! This is an addictive hobby, but one that is very relaxing.

Here is a link that might be useful: The Water Garden

What types of containers are these? I'm just a little confused why you need both the container and the liner... Is this going to be an inground pond? That'll make some difference in your climate, but probably not much. But it needs some consideration none the less.
In a 100 gallon pond, I'd say you can get away with a pretty small pump. 200 gallons per hour (will this be led up a slope, used for a fountain, or simply recirculating the water?) will be enough to turn the water over twice per hour, which is the reccommended minimum for proper filtration. I would not go above a 400 gph pump, as it will cause too much current for your fishes and plants to be comfortable.
A pond CAN be a self contained environment, meaning, you can put a sponge filter on (most small pumps come with a small sponge attatched to the intake which will be adequate), I've even heard of small ponds not having not having any mechanical filtration, when they are planted heavily with oxygenating plants and scarcely populated with fish and wild life.
A pond that size, I would not put in commets or other fishes that can grow large. Commets are set to grow up to a foot in length and your pond would be very uncomfortable for them to keep them healthy. The fancy goldfishes, however, could be very happy there if you get a smaller variety. The variety of fish you expect to keep in winter, will depend on how cool the water gets - and this is where inground or above ground can play a part.

Good luck with your pond, Nancy is right, it can be extremely addicting!

The container that I have is a very thick tree container. I have sealed up the drain holes and cracks, and it will need to be lined because the sealed walls may fail with the water weight. I have designed a frame that will support the weight and keep the pond from failing.

It will have a fountain sprayer.

I will have Submerged,Floating, and Marginal type plants. As for the different types, I do not have a clue.