I swapped my chips and didn't lose my scores. Not sure why? I got my chips from John Wart. His instructions are below.

"Installation is not difficult; the key is to make sure the new chips are installed with their notches pointed the same direction as the original chips were - the notches determine polarity and if installed backwards, will ruin the chip.

The CPU ROM goes on the CPU board, the sound ROMs go on the sound board.

Installation instructions for the CPU ROM are here:
http://thatpinballplace.com/documents/installing_eproms_wpc.html"

I didn't need to remove the board either. Just make sure the notches are right. My first attempt was backwards and I had to pull and re-insert. Very lucky my chips are ok. Also, after install, everything in the switch matrix column 3 failed test except the borg ship. This caused all of the poppers and guns to fail. After hours of investigation, we determined the CPU had shut the column off as it thought it was broken. Apparently, this is also common on WH2O. All we had to do was set off the optos in the column and they passed the test again.