Re: Splitting assests, lawyer or not?
Mediation is fine if you are in the ballpark to start. It sounds like you are. Few divorces are decided by the judge. Usually the parties come to agreement outside of court, even if they've had expensive lawyers arguing in court. Know what you desire, know what would be acceptable, and know your absolute limits. Go to the mediator and start by asking for the moon. Then listen to her proposal and negotiate. Worst case is you don't find agreement. But you may resolve at least some of the issues.
Our mediator provided some information but it was not legal advice even though she was a lawyer. Things like "this is a typical way of calculating what it is worth", or "judges are typically happy with this but not that". So there was some guidance to keep us within bounds, plus of course providing the structure and safe space to discuss productively.
Generally you should end up pretty close to 50/50 on the net worth. Add up all assets and subtract all debts. Divide in half and that is what each of you get. In your example the truck counts as $14,000 net towards your half of the assets. Don't get caught up in the gross value or the loan balance, look at the net. Loans go with the asset, so car loans go with the car, mortgage goes with the house, etc.
Retirements are a bit tricky to calculate exactly, but generally you would get half of what it is worth today. If it is a 401k or IRA account then half would be transferred to your 401k or IRA. You can get burned with taxes if you don't transfer them directly. If it is a pension then you may need professional help calculating present value of the future expected payments. Taxes on investments and realtor costs on selling the home are details but probably not big numbers, so it may not be worth paying a CPA to figure those out. The mediator may give you some guidance on whether your situation warrants accountants.
Having said that, there is nothing wrong with you hiring a lawyer to advise you from the sidelines. Even without your stbxw knowing about it. That is what I did, and it did help me negotiate with more confidence.
I highly recommend having a lawyer review all documents before you sign anything. With minor children involved it is important you get the documents airtight.