Changing the Vyper/Gekko battery is simplicity itself. Battery is about $2.50 at Walmart. Just be careful with the O-ring. Be sure that it is not damaged, and that no foreign matter (salt, hair, etc.) is stuck either to it, or it's seating grooves. Replace it if you can find one. Use a light (just shiny) coating of silicone grease. LDS wanted $20 for a Vyper kit, which consists of a battery and O-ring. $17.50 seemed pretty pricy for an O-ring, so I have reused my old ones several times. I reused O-rings in my Nikonos' many times with no problems. Static O-rings, if not damaged, last a long time. Follow the instructions in the manual.