The area where it "looks" chewed up appears to be where the belt is clamped together. It uses a small metal thingy to hold the 2 ends together. In my opinion the machine is very nice but maybe a little pricy. I might see if they would come down a little. The cabinet looks complete but I can't see the whole thing. Its got a lot of wear spots where the finish is missing so you may be able to use that as a bargaining chip depending on your location.
Belts can be had for less than $10, bought mine locally for $6. As far as attachments and what not, Macybaby would be the one to chime in on that question.
The TreadleOn website can tell/show you what to look for when researching the vintage/antique machines. Once you have one machine others will be popping up at an alarming rate. The things are worse than potato chips.