Well, FAM worked for me pretty fine with upgrading mp-community-fremantle-pr only. For CSSU-Testing and for CSSU-Thumb.

As FAM and HAM are only GUIs for apt-get, there's no real difference between them. (only that FAM is better, when HAM reboots system after upgrade). So there's no point in choosing HAM or FAM.

If you have kp50 (no u-boot), kernel-cssu-flasher. If you do have u-boot, you'll have to work with booting of the kernel-cssu-bootimg (or there's already working image, i don't know.)