Greetings! 1999 GMC Sierra Z71 with 233,000 miles

Had fuel tank removed to check something on fuel pump module that I replaced about a year ago. When tank was removed, noticed sound of something rolling around inside. Remove fuel pump module and found rollover protection valve lying loose in bottom of tank. Have looked in the book and can find no info on repair/replacement of this component. From outside of tank is seems to be an integral part of tank. Have tried to reach into tank and see if part would just pop back on but cannot reach. My question/s are is this a replaceable part without having to replace complete tank? Is there any method to remove from the outside of the tank? And finally what affect other that it's obvious function will leaving this out have on operation of vehicle? Any info would be appreciated. Thanks!