I went through a mediated divorce in California. I had my own separate lawyer on the side, as did my ExH. That was really important as they could give me an objective opinion on what I might expect and whether the things we discussed in mediation were fair or appropriate to me.
It really didn't add that much to the overall cost to have the outside lawyer, either - I only needed to see him a few times.
You should see a lawyer to get a clear idea of what you should ask for in mediation - basically, the idea of mediation is to agree on what the courts would probably award anyway, and save the hassle and expense of going to court. Don't let your ex use it to bully you into an unfavorable settlement - go in armed with information.
Here in California, you're right, the alimony and child support are pretty standard calculations usually.
Find out if there will be tax consequences of your short sale.
Legal separation costs as much as divorce in California, really no point to it.
At a certain point, you may need to file just to preserve any assets that are left (like 401ks).
