Are they the same or is there another wording that is しないのでなければ? What does the latter mean? Does the するの in the front imply that it's something that has already been done? I'm interpreting it as something like "if it weren't for" from the way it sounds but I'm not really sure about it. The more I think about it, the more it seems like they can have the same meaning.
するのでなければ is the same as しない(の)なら(ば).
For example, 日本へ行かなければ富士山は見られない means only after you go to Japan you can see Mt Fuji, while サンフランシスコへ行くのでなければ花飾りはいらない means you don't need flower ornaments unless you are scheduled to go to Sanfrancisco.