I'm interested in the following kind of questions about groupoid $C^*$-algebras.

1) If $G_1 \times_{H} \ G_2$ is a fibre product of (nice) groupoids do we have something like $$C^\star(G_1 \times_{H} \ G_2) \cong C^*(G_1) \otimes_{C^\star(H)} C^*(G_2) ?$$ 2) Of course, in general, there is an ambiguity about the above tensor product. So what is a good notion of amenability for groupoids? (In the sense that the groupoid $C^*$ algebra of an amenable groupoid is nuclear.)

Apart from Renault's classic about groupoid $C^*$-algebras I do not really know any other reference for this subject.

Thanks!