Cool. Almost all of your travel between the cities will be by bus. Set your expectations very, very low, haha. They will run slow and be very poor quality. Expect that, and you will be pleasantly surprised rather than unpleasantly surprised. I imagine that you'll just take a straight line from Vientiane, Vang Vieng, then Luang Prabang.
However, I make the standard plea to anyone heading to Laos is to check out the Plain of Jars. Between Vang Vieng and Luang Prabang you take a road east to get there. It's kind of an ordeal, but definitely worth it. Learn about these mystery jars, experience an amazing archaeological site basically by yourself, and learn about (and see the destruction from) the largest bombing campaign in human history. Totally worth it.
As far as travel is concerned, it's pretty standard and is all covered by WikiTravel. Good luck!
Check out wikitravel: http://wikitravel.org/en/Tha_Khaek#Sleep
Just ask them for longterm stay discount. Thakhek in general isn't too touristy and you should be able to leverage that given the fact they'll have lots of empty rooms regardless.
I know there's a hotel right in the center at the intersection with the red lights.
https://www.amazon.com/Lao-Beginners-Benjawan-Poomsan-Becker/dp/1887521879 This is probably the best one of the limited options, although there are likely more options in Vientiane than Amazon, at a cheaper price. However, this may be a little below your level if you have a basic understanding. This may help you learn the alphabet, apthough I think that having a tutor/instructor would make that part easier. In Laos there are also books for students focusing on how to write, different consonants and vowels, but I don’t know if those are available outside the country.
Here are the store links if anyone is interested! :)
Apple iOS store: https://apps.apple.com/us/app/the-kwanstone-project/id1633568879
Google Play store: https://play.google.com/store/apps/details?id=com.SIPSONG_STUDIOS.TheKwanStoneProject
Awww! Well if you are ever down there again, this is the exact location.
Tad Yuang waterfall Location: geo:15.180355,106.13853?z=18 https://osmand.net/go?lat=15.180355&lon=106.13853&z=18
So my fiancé is Laos, and I'm learning Lao (primarily so my future kids can't talk smack about me behind my back lol)
Definitely going with the whole practice with people.. But I found this app helpful for review on vocab, even my fiancé learned a few new words. https://play.google.com/store/apps/details?id=simply.learn.lao
"Culture Shock! Laos: A Survival Guide to Customs and Etiquette" is probably the best book for what it seems like you're looking for.