I asked my IC this once (not being a lawyer but having lots of experience with lots of people who ended up D from his therapy practice). He advised me to assume an average of $14K per person (Northern California), once it's all said and done, all expenses in. The typical L around here wants a $5K retainer to start, $8K for an unemployed SAH parent. Remember these processes sometimes can take years, so it could be as simple as filing fees and doing it yourselves at your kitchen table, or lots, lots more. In general it depends on how cooperative you *both* are (and you can only control yourself).
The problem you haven't thought of is that infidelity is already a serious breach of trust, and KISA syndrome notwithstanding, the hurt party needs to be protected more than the predator. Someone wise here in SI said to me "You being here means she didn't give you a fair M, what makes you think she'll give you a fair D?". That's the best argument for being protected I've heard.
There's also collaborative divorce, where the Ls are less adversarial. Like my L said, "just pretend you're both just winding down a business so you can close it - it's really just assets, income and expenses."
I moved out of my house. My mental health was worth it, and it's better for the children not to see the fighting. As a man, you need to be very aware of the very real possibility of her accusing you of DV, particularly if she has no leg to stand on (sure, uncontested D and all, but if there's conflict and God forbid it ends up in front of a judge, the judge is going to want to know fault anyway and will only have a few minutes to make a decision for or against a party). Staying in the house makes this type of accusation more, not less, likely to happen. That's why you want to talk to a L first, regardless of what you do. I don't know what the deal is with nesting, but DD8 and DD10 have adapted very well to the two houses situation (if you're both good, involved parents, it shouldn't be an issue).
Moving out in my opinion also helps on the budget - how can you possibly know how much you can afford in alimony and support if you don't know your living expenses, your rent, your utilities, etc? Remember these orders can be hard to change once they become permanent - judges love something called the "status quo". You want to set the status quo to something you can live with long term as early in this game as you can.
Many Ls will give you an hour consult for free to get a feel for them. Make sure you take advantage of that. Talk to more than one.
Remember, even if it's uncontested, even if it's mediated, you have a right to legal representation. The L can be as involved or as uninvolved as you want him to. For example, it can be as simple as you draft everything yourself together (if you get along so well) and then send it to the L to "red-line" before signing. If you're the main wage-earner, you need legal representation.
If STBX balks at you getting a L for reviewing paperwork, be very aware that the reason could have been that she was intending to control the whole process (of all these D discussions, who was the originator of the idea?). This happened to me, as soon as she found out I paid a retainer, she freaked and wanted a full blown D, and got a more expensive L herself, a clear sign that her intent was to railroad me since I have been way too nice for 18+ years. As the first batch of bills after I moved out came up, she sent me a nastygram regarding "the mother of your children being taken care of". But since I mostly didn't engage, the Ls restored civility fairly quickly.
Hope this helps. We're all learning stuff we never wanted to know here in SI.