[shoguning]

All I can say is, good luck.

I discourage everyone from doing a PhD, but it sounds like you've made your mind up.

Be very careful with your choice of advisor and department, and if it isn't working, be ready to walk away--sounds like you have a career to go back to.

[glial]

Having just finished a 10 year PhD stint, I second this advice. It is absolutely critical to have a supportive department, secure funding sources, and an advisor with whom you can work well. If any of those is not the case, it’s a recipe for a bad time.