A lawyer will often delay the process, simply because it's an extra step that adds time. Example - you get your Welcome Letter once the case reaches NVC. If you receive that directly, you probably log on and start the visa application process the same day, pay the fees immediately, etc. If the lawyer gets the letter, it may take them a few days to let you know it's arrived and forward it on to you, and then again a few days to tell you the payment has cleared and you can start the next step. So that thing that would have taken one week if you did it, potentially takes 2 or 3 weeks.
I would just submit your I-130 asap (it's not complex, you could get it submitted this week with the help of VJ on anything you're not sure of), then that starts the clock ticking. Then once that's in, you can start reading up on the rest of the process and understanding the next steps, and start gathering the documents you'll need to avoid any delays at the NVC stage. https://travel.state.gov/content/travel/en/us-visas/immigrate/the-immigrant-visa-process/step-1-submit-a-petition.html
Best of luck.