The specs for this double oven give a rating of 5.1kW at 208V so it needs a 30 Amp circuit breaker. This assumes that the oven is the only appliance on the circuit. So you should be able to use the same circuit breaker.
A bigger consideration is that the opening for the double oven needs to be larger than that of the single oven. If the opening does not have a solid bottom, it must be able to support a heavier load. The runners and braces under a single oven has to support 200 pounds (91 kg). A double oven must have braces and runners designed to hold 375 pounds (171 kg).
Also check if your household uses aluminum wiring. The new oven has copper and problems will occur at the interface if you do not use the appropriate precautions. (Products designed for mating copper and aluminum are available - follow the directions).
I hope this helps.
(btw: you can find the User's Guide and Installation manual for the double oven at GE's website: http://products.geappliances.com/ApplProducts/Dispatcher?REQUEST=SpecPage&Sku=JKP35DPBB
. See the section Literature and Manuals on the left hand side of the page below the picture of the oven.)