I have an acoustic guitar, Epiphone, Ft-135, block inlay. Blue label inside. It’s in good used condition. No scratches, dents, etc. Also have original receipt dated 1973 and original lined hard shell case.

Would like to know how valuable it is. Is there a site online or guitar forum that can help with this? Do I take it to a vintage guitar shop? Do they normally charge for estimates?
Thank you.