I went to have someone "reputable" out of Ann Arbor to re-build my chimney cap and re-seal the mortar above the flashing... and they showed up with some smear on crap and wanted to charge me $800 for it. I told him to put down the caulk gun, gave him $50, and told him to get the fuck off my property.
I sat there with an angle grinder and ground off the old cap, scrubbed the chimney with a tire brush and Scrubbing Bubbles, built a new set of forms, poured a new cap out of high temperature cement/concrete, and applied the sealer myself. Would have gladly given someone $800 to do that.
10 years later and it looks like brand new, except covered with creosote from burning 11-18 face cords of wood every year.
One of the few things I was going to hire a "professional" to do and regretted wasting my time. So yeah, find someone that doesn't suck.