Default Switching Phone numbers at Sprint ???

Im jumping to the M8 this weekend and turning over the m7 to the wife. Considering ive never done this before( always retired the phone) When i take it in to change it over to her number, will i need to RUU or can I just leave the Rom Im running presently on the phone.?
Devices: Sprint HTC Hero200 CDMA,Sprint HTC Evo 4G Supersonic,
Sprint HTC Evo 3D, Sprint HTC Evo 4G LTE, Sprint Htc One(M7)
Present Device: Sprint Htc One (M8) Harmon/Kardon Edition
Recovery: CaptainThrowback's TWRP 2.7.0.7
Rom: InsertCoin
Kernel: MassStashedX-0.19.1
ExtSd: 64g Class10


If I've helped you in some way, Keep it to yourself or all the kid's will want some,,,