Apparently frozen focusing due to hardened lubricant is to be expected with many of these old front-element-focusing folders. If I recall correctly, I read somewhere that using lighter fluid (caution--extremely flammable!) will sometimes resolve the problem, but it may take a long soak. I tried it once with the lens from an old Ansco Speedex, but even after several days of soaking, it was still frozen so tightly that the force I used ended up cracking the element. Glad it wasn't an Apo-Lanthar!
There is a gentleman in Pennsylvania, Jurgen Kreckel, who routinely refurbishes old folding cameras and then offers them on E-bay. If the photos are any indication, he does a great job.
Here are a couple of web sites for further information:
In addition, kyphoto.com/classics/forum/ has a ton of postings about specific types of camera repair problems.
Hope this gives you a starting point.