Help with mixlogit

I am new to Stata and specifically to the mixlogit command. I am trying to work out a model and have two main questions:

1. How can I derive the marginal effect of an independent variable after estimating the model?
2. Is there a test I can run to prove statistically that the model obtaied is better than a simple conditional logit model? I tried to run lrtest, but it does not work when comparing clogit and mixlogit models.

Thanks in advance,

Carlos