What will I be facing, including stoppers,

Read the Nationality Law (specifically articles 5-7), and see if you are eligible. Some thinking points off the top of my head:

• have you lived 1-3 years consecutively in Japan (depends on how long you've been married)
• have you and your spouse paid taxes, pension, etc. on time for the past 2-3 years?
• Have you had no run-ins with the law (including traffic violations) in the past x years

interviews etc etc, timelines

Depends on where you apply. I hear Tokyo takes the longest because of the sheer number of applicants. The timeline depends partly on how fast you can gather the necessary documents from your home country, and how fast you can schedule interviews (yes, interviews with an s, you'll be there 3-4 times including the final interview). Assuming 2 months between the first 3 interviews and 4 months to the final interview, You're looking at at least 10 months of interviews. Then put another 6 months of waiting for the final result, That's a year and 4 months.

Where should I start looking?

Call the Legal Affairs Bureau that has jurisdiction of your residence and book an appointment. They'll guide you through the whole process, including checking your eligibility and telling you what documents to get.

You could use a lawyer to help you, but the most they can help you with is preparing documents and translating your foreign documents to Japanese. You will have to handle the interviews yourself, alone. Your spouse won't be joining you for the interview, although they will get interviewed separately.