Trogdor the Burninator,
considering the nature of the inquiry, i dont think this guy is up to disassembling the unit or playing around with tv tuner cards. also, almost nobody actually uses a true EPROM chip (write once) but rather flash memory as it's cheaper and upgradable. in short, you should be able to rewrite to the chip without needing to extract it but use some careful wire connections. if all else fails, buy a DVR that does what you want.
"the wisdom of the wise will perish, the intelligence of the intelligent will vanish."