I have no idea on the min size hd. for the cd rom, there are a few ways to connect, the easiest (imo) is through a scsi controller called squirrel made by hisoft (don't know if there are any other makes), this just fits into the pcmcia (creditcard like) slot on the side of the 1200 with a cable that you can connect to an external scsi cr-rom, it's (well it was for me) just a case of plugging in, installing software and away you go. I'm not advertising here, but I have 2 squirrel controllers, I don't use the miggy for anything online, so I may be willing to part with the surf squirrel at some point soon. I'm pretty new to the miggy (well, after an absence of about 6 years) so sorry if I can't be more help or my advice isn't best, I'm just going by what I actually know, not what I have heard/seen on other boards etc)
