Hi, chinito:
1. If your s-parameters are for 1-port, you can just convert it to Z11 and fit it as Z11 = R + j omega* L.
2. If your s-parameters are for 2-ports, you might want to convert it to Y parameters. Then, you find Z = 1 / Y12 and fit Z = R + j omega * L.
3. I don't think you can separate L into different parts. Different parts are just for some kind of explanation. S-parameters are from the overall results. It includes the effects of all the factors. You just can separate teh effects into different parts.
Regards.