5100cn losing network connection

hi all!

    I have a dell 5100cn laser printer that will lose network connection after a short while being turned on.  To get it back I have to power off/on, then it's fine for a while.

   I cannot ping, bring up printer status remotely, nor print.

 However, I can print the printer status from the printer itself and it does show network IP address and looks like all is well.

   I do have link light on the NIC at all times.

 Is the NIC replaceable in this old gal?  She prints really nice still and I don't want to get rid of her, I'd rather repair her and keep her going for a while ;-)

thanks all!

   Mike B