River, I’d say start with the yellow pages, and look under bookkeepers. You could also talk to someone at your bank if it’s a big enough sum. The other source is to talk to someone you know who has their finances handled, and ask them who they use and who they trust.
There’s a ton of financial systems and software out there, lots of them quite good.
The question is always, like all the kinds of diets out there and exercise programs, can you stick to them? You want to pick one system and then stick with it. Ah, there’s the rub. But like so many strategies for ADHD sometimes part of it is simply building the routine and making it easy and accessible.
Like if you have a system that requires you to write out all your expenses at the end of the day, then put the ledger book where you write the numbers on top of your pajamas, or your pillow. Maybe put a big post it over your bed to remind you. (At least for the first few weeks, until it becomes a habit.)