1) It will work but only work at SATAII speed, but you only see the differences in benchmark between the SATAII and SATAIII, and you will not feel the differences in real usage.
2) If the win8 is full version, you just plug in the SSD, set the AHCI in the bios and only connect the DVD too, boot up and install the win8. If the win8 is upgrade version you need one OS on the SSD before you can upgrade.
3) Yes, TRIM will be on because TRIM is only effective on operating systems which win7/8 support it.
Useful SSD Articles - Part 2 http://www.tomshardware.com/forum/270102-32-useful-articles-part