I have a solution! You have to get reference to the VM you just added and then configure the network. Turing it on is pretty easy after that.
$vmRefs = $sdkVApp->getContainedVmRefs($newVmName);
$sdkVm = $service->createSDKObj($vmRefs[0]);
$service->waitForTask($sdkVm->modifyNetworkConnectionSettings($nsection));
$service->waitForTask($sdkVm->powerOn());