You can contact a furniture store that you like and start from there with their recommendations. Interview 2 or 3 for sure to see who you find is on the same wave length as you design wise then ask for references and pictures of projects they have done. Make sure these are designers and not just decorators there is a huge difference, you will need someone who understands plumbing, electrical ,structure so be picky.

I did the exact same thing in our fixer upper.. but I did it all myself.. I am posting pixs in the before/after... parts were structural (removing beams, gutting bathrooms), others were paint, flooring, etc... one thing you need to bear in mind, is the budget.. it will go up, since you may find 'issues' in 1970s houses (we had carpenter ants grooves, rotten wood).. I started by making ideabooks in houzz.. and certain images stuck in my head.. so I tried to get those elements into my spaces...

Many of my clients have found me (and other designers) right here on Houzz, under "Find a Pro". I would read reviews, look through portfolios and then email a few and see how they respond. Before you even take the time to meet with them I would confirm what they charge. You're likely to see rates from $40 - $200 an hour and everywhere in between. Hope that helps!

Here are some after pixs..

Wow! Great job doing all that yourself!

Hello! Houzz is certainly a great place to start when looking for a designer. They have a huge listing of designers throughout the country in the 'Find a Pro' section. If you'd like someone to come out to your house in person that would be a great route to go. Another option would be to use an online interior design company, such as ours. Basically, you send us all of your information and we send the design concept/layout/furniture plan/etc. back to you through cyberspace. This is extremely cost effective (usually much more so than an in person designer) and it's a lot of fun, too:) If you're interested we'd love to help you out! If not, check out the reviews in the 'Find a Pro' section. You're sure to find someone great there!

you can do it too... I believe design has to be functional - no point having a beautiful house that accumulates clutter quickly (because of layout issues), or is just 'showy' and families cannot 'live' in it.. families are busy.. design needs to take that into account.. :-)

See work that they have completed and make sure you like their taste and they don't force you to like something just because they say it's nice. If you think you don't like it you probably won't like it five years down the road.

Yes, shop around. Space utilization is not only a specialized skill, but also depends on talent and experience. Check out work by the person you're considering, and think about whether it flows well and is consistent.
You also might want a different person for kitchen and bath work, depending on your needs. Often, a design/build company works well for a project like yours.