You have what’s called Lionel tinplate O Gauge track that the original Lionel Corporation made before 1970 in New York. As you’ll notice on each of the 3 railroad ties that hold the rails in place, they have a stamp on them that say Lionel and NY. That size railroad tie distinguishes the difference between O Gauge track, and O27 track. O27 is the same width as O Gauge track, but it’s railroad ties are smaller in height, and the rails are a little thinner. When you make a complete circle in O Gauge track using standard curve sections, it will make a circle 31 inches in diameter, and requires 8 pieces of curved track to make a complete circle. O27 track requires 8 pieces of curved sections as well, but it has a tighter radius diameter of 27 inches. So when you purchase track, make sure you ask for tinplate O Gauge track. You can find this track at any good Hobby shop in your area that sells Lionel trains and accessories. If one is not easily accessible to get to, you can always shop the Internet such as a Trainworld.com, Charles Ro Supply, Grzyboski Trains, etc etc, or you can go on eBay.com and search Tinplate O Gauge Track, or even VINTAGE O Gauge track and find some good original tinplate O Gauge track that was made made in the USA back in the day, and not in China where they’re made today. (Vintage track actually feels a little stronger and sturdier than current production made tinplate track) Either case, that’s what you want to look for to match the track you currently have, that originally was your Fathers’ when he was a boy. Do not be talked into purchasing the new Lionel Fastrack. It’s beautiful track, but it’s not compatible with your Tinplate track, unless you purchase an adaptor track they produce and then purchase all new trackage. It starts to get costly at this point. Stick with what you have. It’s still great time proven track and full proof. I use it myself for my 2 running holiday train displays every year. I just says Lionel to me underneath my Christmas tree.
I hope this helps you out. Tom

If the insulation of the original wire is not exposed or brittle, then yes, resoldering can be a good thing. Old solder does sometimes break away or becomes lose and your electrical connection is impaired. And since you have it apart, it would be a great time to give it a really good cleaning and oiling. Check the gears for any hair, fur, or lose material and remove with pointy tweezers. Lubricate the gears with a light grease that you can purchase at your local hobby retailer, or online through eBay. Lionel sells a lubrication kit with grease, oil, and track clean. That might be your best bet to purchase. When you’re all done, your locomotive should operate like brand new when it first came off the assembly line. Please advise how your project turns out. It will be a fun thing to do, and self gratifying. Happy Thanksgiving!!