You do not lose any total Xper points and your Xper level does not go down. Your redeemable Xper total will change to reflect that you've redeemed points, which can be seen on the Xper tab of your profile.
No. Your overall total that shows on your profile and your xper level will not drop. Only your redeemable total will drop. If you go to your profile and then go to your xper page, under the bar that says "Redeemed Xper Points" at the bottom it should say "Redeemable" and have a number beside it. That is the amount of xper you have left to redeem. However, as I said, your level will not decrease.