Stochastic Discount Factor on Excess Returns

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Hi,
I try to find risk factor prices for carry trade strategies following Sarno/Schmeling (2012 "Carry Trades and Global Foreign Exchange Volatility") using the SDF approach.

I have constructed 5 portfolios, and have their monthly excess returns over a period of 23 years. Further, I have 3 factors and I am trying to get the risk prices for that. The Fama Macbeth approach is easily done by the eviews add in, but I want to use GMM for estimation of the parameters as well.

The SDF approach:
E(m(t+1)rx(t+1))=0 M is the SDF; rx are the excess returns
m(t+1)=1-b'(factor(t+1)-factor(mean)) b is a vector of factor loadings.

Here is where I cannot continue. Is b the factor of beta estimates? In other papaers, it is the build by Covariance Variance Matrix of returns and factors (which effecteviely is are the betas?!) But still, I dont know how to estimate this b vector.

The SDF approach then implies a beta representation of the model:
E(rx(i))=Lambda * ß(i)
Lambda = VarCoVarMatrix * b; ß is the times series regression beta.

My problem is to find b estimates and the right VarCoVar matrix.

I am not that familiar with eviews and this approach.
I am thankful for every answer.

Best Regards