A warm welcome to you Charles. Happy to have you here and delighted that our forum is the first you've ever tried. Once you get the hang of it, it will be a piece of cake. Remember, if you ever need help, try our HELP section. It should contain most everything you need to post. If not, leave a message in the help section and one of us will jump in to assist. 
I will be more than happy to look into 539th and see what I can come up with. It will probably be a couple of days because I am going away for the weekend.
Unfortunately your story keeps occuring again and again. Not knowing, not finding out until it's too late. You'd be surprised how many times I have heard this. Very sad. 
Hope you find our site helpful and once again welcome. 
Proud Daughter of Walter (Monday) Poniedzialek
540th Engineer Combat Regiment, 2833rd Bn, H&S Co, 4th Platoon
There's "No Bridge Too Far"