I'm mostly a PC programmer so I'm definitely not an expert on programming these boards. Its just a hobby for me.
They come fully assembled. It's a great price for what you get. Go to the Freescale website for the details on the processor. I'm going from memory here but I think it has 256K of flash (Freescale also has a 512K flash version), 2K of EEPROM, and 12K of RAM (it may be 8K RAM - but it's quite a lot).
These devices are very memory-efficient so I've never used more than 4K in my own little programs.
The devices with d-bug12 are used to develop programs that get downloaded and run from RAM. You can set breakpoints, trace, etc. But it's harder to program flash with these devices because you have to use the bootloader and overwrite d-bug12 itself with your program. Most colleges use d-bug12 because they like the debugging features and they don't need to program flash, anyway.
If you know you'll need to use flash you can use devices in the new
9s12Cxxx series because these come with a serial monitor that makes it easy to program flash. My IDEs can download programs to flash using the serial monitor but I don't support interactive debugging yet. Technological Arts has a free program called ubug12 that has some debugging support for the serial monitor.
The commercial CodeWarrior IDE is much better than mine and it comes in a free version that works with up to 8K of memory, I think.
Eric