making a new RFID reader vs. modifying an existing one

[ssylee]

I'm trying to decide whether it would take less time to make a new
RFID reader using an antenna from an existing unit as well as using
the code (to produce the fsk signal) as well as the circuit used to
match the antenna's resonant frequency. The existing unit is made of
an antenna made out of coils of lacqured copper wire. There is an
existing unit including the firmware codes for the microcontrollers on
the unit, but it doesn't talk properly anymore to the computer. It's
also built for a slightly different purpose too. It's built to
periodically check for the presence of a tag and then report to the
host computer. I'm trying to get it to communicate either to another
microcontroller, or to the host pc and have it coordinate between
talking to two separate microcontroller systems. I'm also thinking of
building a new one with a separate microcontroller system or RFID
reader, adapt the code used for the existing system and have it to
talk to the host computer. I'm wondering in your opinion, based on the
information that I have found so far, whether fixing the current
system in terms of hardware and firmware-wise despite its reliability
issues or building a semi-new one adapting some of the circuits and
code of the existing reader would be the easier and more reliable
solution. Sorry if I still sound vague, but your views would be much
appreciated as I have more point of views to work with.