Don't forget that you don't have to rely on the c-code version of the simulink model, and that you can import the .mdl file directly (with the MIT). The success of the conversion depends upon the exact nature of the original model - e.g. discrete or continuous time, graphical or s-function, and how you want to realise the final model, e.g. within LabVIEW's CD&SIM or in some more primative construct (e.g. timed loop for discrete model).
We did a model conversion where the original model was s-function based, and the easiest way was just to copy the various parts of the s-function into several appropriately connected Mathscript nodes within LabVIEW.