Because your gen2 chip was only installed recently you should be able to have it removed fairly easily since there isn’t much chance of encapsulation to have completed. You should be able to install the gen1 replacement chip directly into the pocket left by the gen2 removal procedure.
Risk of infection is always dictated by what you’re putting into your body (is it clean?) and the procedure (did they contaminate the incision?). If you’re worried, you might approach a medical doctor about removal and/or replacement… or at the very least removal (any GP could do it), and then get a modder to install the new chip with a needle procedure later. Though once the chip is out, sliding the gen1 chip into the wound should be very easy. Keeping it in place will require a pretty tight bandage, since you’ve conceivably made a much bigger hole to get the gen2 chip out than the original needle made to get it in there… so insist the practitioner apply some tight steri-strips over the incision site to keep the thing from flying out.