There is no official release of 4.5 for the 8830, just betas. I would wait until it is officially released, but that is just me.
What state is the device in? Does it load at all? is it stuck on a jvm 507 error?
Start with removing everything from the device : How do I wipe the BlackBerry using Jl Cmder? - BlackBerryFAQ What to do next if Jl Cmder will not connect and wipe - BlackBerryFAQ
Once it is wiped, try loading the most current officially released OS for your device: http://www.blackberryforums.com/gene...ge-sprint.html
Follow the directions in the links and you should be good to go. Best of luck to you