The poppet spring and balanced chamber...snip....each no more than couple of dollars.
Please share this information. Where can one purchase any of these items for "no more than a couple of dollars?" I cannot even find a seat for $5 much less a poppet assembly for much under $20.
BTW I agree updating the OP's G250 to the current valve components is a good idea. But unless he is armed with decent information, a LDS may try to take him to the cleaners.