I don't think there is a LabVIEW 7.5.
Fitting multiple peaks is necessarily ambiguous because there will always be multiple solutions (e.g. swap all parameters of two peaks and you'get an equally good fit). It will be important to have good initial guesses.
An amplitude alone does not define a gaussian peak, each peak also has a position and width so you'll have to fit three parameters per peak. Is the number of peaks fixed or can it be variable? Do all have the same width?
The nonlinear fitting VIs have been extensively revised with LabVIEW 8.0. Doing the same in LabVIEW 7.x would involve quite a bit more work. LAbVIEW 8.0+ even includes an example that demonstrates fitting a function that is the sum of three gaussian peaks plus an offset. :)That example would be a good starting point for you.