I'm not sure if you got the actual answer on your chain question. Chains have two methods of connection master links and riveting. Master links have a side plate that can be removed. Look at the chain and see if there is a link that is distinctly different. You push the sideplate off and then you can remove the rest of the link, literally no tools required. Riveted chains need a chain tool. The one to get is the park one.
Chain size on bicycles really depends on era as the mfg. made them narrower and narrower to add more speeds in the same amount of space. So how many speeds is this bike (that's the number of gear sets in the rear cluster), that will define the chain you need. But realistically unless you live in never never land just run by the local bike shop with the old one and they will sell you the correct new one. Once you have it you have to cut it to the proper length and then reinstall it by a master link or riveting. hope that helps.

SigForum is an amazing place for getting clear, concise advice from people with more experience than the OP.
This seems to be a remarkable exception. Sorry about that.