What do I need to read/recover data from the hard drive of an Apple II CX? My father bought an Apple Macintosh II CX in 1990 and it survived until 2010, when the main harddrive broke down and despite trying multiple times, booting from floppy disks failed for an unknown reason. 

The main concern is the external 800 MB SCSI harddrive that is intact and hosts files that need recovery. 

What kind of hardware and software (PC/MAC/Linux, anything goes) would be required to extract the data from the external hard drive? If there are several ways, what's the cheapest one?
Wait and buy a used Classic mac with a SCSI port that works. Also Ultra SCSI cards for PC's go for $25 to $50 on the internet, so you could go that way with a cheap PC or borrow one.

Any computer can image the drive into an ISO CD image so you can get it to a Mac to mount the filesystem and read things.