Regarding the crossover cable ... pretty much any Mac that is still useful will not need a crossover cable. Any old ethernet cable will do since Macs have an auto-detecting ethernet port. The PC probably has one as well.
As for an external HDD, you can get around the Mac/PC issue by formatting it in FAT32. Both the Mac and PC will read/write to this format, but the largest file size allowed will be 4GB. Alternatively, you could format in NTFS, which the PC can read/write and the Mac can read. Should be enough to allow you to transfer to the Mac.