It looks like the Sintron kit comes with some pdf instruction files you can request to download after you purchase the kit. I didn't see anything like that with the other two you listed? Sometimes the written documentation from the Asian ebay sellers is almost unreadable and makes very little sense if you can read it. I can't say about these as you can't look at them first?
I got a starter kit form Sparkfun a few years ago. It came with a pretty good instruction manual showing the wiring diagrams and explaining the operation of the experiments. As I recall they also had downloadable files with the code so you didn't have to type it all in. And also had any needed extra Arduino libraries available for download for the projects. Seems like it was $49 or $59 for that kit when I got it. Could have been on sale too, I forget exactly, it's been a while.
Anyway, you might look at Sparkfun, Adafruit and the Arduino websites for their kits. The documentation might be worth the extra $$ that they cost, especially when just beginning. There are other books out there, but these vendors have written the book to match the projects in the kit which might also be of assistance. Adafruit also has downloadable files for their projects and Arduino may also have them, I am not sure on that one. There is a lot of good information on the Arduino site and als the others as well. All geared for the electronics hobbyist. They want you to learn so they can sell you more stuff, just like the train manufacturers. 
