the older varieties are much hardier, the dwarf, and I use that term loosely as they can get to 10`, are not as hardy and probably will die for you. Hardy red is the hardiest of all, it`s a big one. There is an older white that is about the same size and almost as hardy.

I would suggest cuttings of the ones that survive. This are absurdly easy to root.
Tally Ho!

How do I root it if I get hold of one?

Check the propagating forum (Or rather, Google, which will then possibly have some result to old threads on gardenweb where someone probably asked about oleander). But in a nutshell, cut some tip of the branch (the kind of branch will vary with the plant, but judging from oleander, it will probably be some new growth that isn't fully brand new but not quite mature into wood either), stick it in some soil mix or your favorite rooting mix, in shade or bright shade, and keep the soil moist until it roots.

Also, I believe oleander have plenty of seed pods in late fall or early winter. Is there any possibility to use those as seeds to plant? I'm asking since I don't really see volunteer oleander plants near the parent, like you might see with other plants that seem to have seed pods like that.

dang seeds are really good at sprouting, usually in the flower beds. They float off.
Take a cutting, 5-8", strip off the bottom leaves, stick it in dirt, water. Any size cutting will root. You can root them in water. You can walk through the yard, stick the cuttings in the dirt and water them. I had them root in a box, lady asked me to hold shipping until she got back from vacation, I forgot about them, 2 weeks later, opened the box to toss them and about 80% had rooted.
I have rooted them in full sun, in the closed up box thrown in the backyard in the middle of summer, in glass jars in the kitchen window.
Tally HO!