Your best team is an architect experienced with single family home remodels and a similar general contractor working together with you. Good luck!

Start with the architect. The builder is a close second. The other team players will become obvious during the process (structural engineer, interior designer, kitchen designer, banker, landscape architect, psychiatrist, . . . ).

Start with a General Contractor. No one has their finger on the economic pulse of the construction industry more closely and it changes daily. It makes no sense to commission drawings of a project that can't be built within budget and we see that repeatedly here.

first, i would go on houzz, yelp and buildzoom and search remodel design/build firms, in your area. send them a brief email describing your needs and follow up with them on a weekly basis. second, if that doesn't yield any possitve leads, then serch remodel contractors in the same fashion, but add that you need a designer involved with the project and ask who they recommend. third, contact relators in your area and see who they recommend for design and contractors. remember, diligent clients who are organized, involved, and responsive, are the best !!! and will attract the best people to help them.

stay inspired

Like @Spire Architecture | SpireBuilt, I'm a fan of design/build where the design part is by an architect.

I suggest you develop a list of all the miscellaneous repair/renovation stuff and a separate list of design criteria for the addition. Then attempt to get a handle on the costs. To this end, either a design/build firm or remodeler would be a good place to start.

Best wishes for a successful project.