do I have grounds for a case? Do I need a lawyer to do it?

I work for Lowes part time and applied for a full time job in which I have 7 yrs experience. I'm 44 yrs old & take medication for attention deficit. When I applied for job the Human Resource (HR) asked if I had any reasons I could not do the job. I said no. HR and 2nd person interviewed me for full time job as an outdoor power equipment specialist , I have extensive training and 7 yrs experience 3 yrs in another Lowes store and 4 at home depot as an OPE specialist. The HR told me would have an answer for me by end of month I went to HR on Feb 3 asking for news re job. HR said the store manager was suppossed to tell me and he was not there that I would have to wait till Monday ! Told me another applicant was chosen, she scored 1 point higher in interview questions. HR said she also had 7 yrs experience with plants and experience in customer service. Stephanie is 25 & she has never worked for Lowes. She worked 8 yrs in a florist shop and 2 yrs in state of Oregon answering phones & etc. In the job description for OPE' s job application it says: "Responsible for achieving weekly sales and margin budgets BY PROVIDING EXPERT KNOWLEDGE IN THE SELLING OF OUTDOOR POWER EQIPMENT, SEASONAL HEATING/COOLING AND GRILLS." This is first words on job description I feel that HR ignored their own job requirements. Stephanie has no product knowledge of OPE, she doesn't even know the difference between 2 cycle and 4 cycle oil.... I have a recorded conversation we had during my lunch break. Stephanie told me in her interview with HR that she thought she was applying for a job outside working with the plants ! Stephanie went on to say that she didn't know that OPE meant outdoor power equipment until we talked. I would like to sue Lowes for age discrimination,my AK Native status, & based on medical/mental condition attention deficit and anything else. Can answer questions & provide details re: my work qualification. When I was OPE specialist my dept was #1 in the Region and # 1 in the distric several times for my sales of extended protection plans.
Lowes regional HR is trying to reach me because I complained to our open door employee complaint number, waiting to get in touch with some attorneys first.
Thank You