39 is definitely not too old! i'm 38 and in my 2nd year of hairdressing at college and i wish i had done it years ago, as previous posters have said, get some commercial experience under your belt as its impossible to see/do everything at college plus you will learn so much from more experienced stylists and improve of your timings etc. volunteering is a great way to get some commercial experience (and a foot in the door) i found that going into salons in person to ask about volunteering opportunities works better than just firing off cv's and letters! once you qualify,keep learning, new trends/techniques come along all the time,in this industry you'll never stop learning! it takes work and dedication but its sooo worth it!
best of luck to you lovey xxx