If you want someone to handle logistics, use a service. But, if your travel is 8 weeks out and all you need is a US passport, pay the fee, complete the forms and provide a copy of your itinerary.

In a pinch, if your location has a Passport Office, they can issue you a passport in 1/2 day (e.g., show up first in the AM and you leave with it at Noon).

With 8 weeks, you should not need a service.