Hi Danny 123, Welcome to the board. Nice machine. Great price.
I'll answer your questions as best I can. First of all. you are half right in your posting. OK more than half , many folks have a terrible time downsizing pics. You got the right forum, but posting it under the Husqvarna post only gets those interested in one obscure magazine. The blue oval called "start new Thread" is the one you wanted.
You could name it "401a Singer questions"
Prices do run all over, but they are determined by condition, location, accessories, phase of the moon , etc.
Your 401a will not run without a controller and as such buyers will buy as a "could easily be broken" machine with smaller offers.
Hand turning the thing will tell you some things, but not all.
putting your (aprox) location may help. Someone here may live around the corner and be looking for one. They can PM you if interested.