Replace Audio Track in MP4

I have a finished MP4 video and a freshly recorded MP3 file that needs to take the place of the existing soundtrack. All visuals are locked; I don’t need color grading, trimming, or graphics tweaks—just a straight audio swap that remains perfectly in-sync from first frame to last... (Budget: $30 - $250 USD, Jobs: Adobe Premiere Pro, After Effects, Audio Editing, Audio Production, Audio Services, DaVinci Resolve, Final Cut Pro, Video Editing)