To be positive I need the set number and the cab number. It appears to be a modern Loco, so I can find the schematic at Lionel. I thought the bulbs were screw type micro. Ebay now carries screw in LED but these are normal size screw mounts or maybe not. A wire lead, 12 volt is sold at Radio Shack, if you want to solder . Options exist and you will have the engines compllete list of part numbers.
The Lionel manufacter # is 6-8702. It is the Southern Cresent Limited 4-6-4 steam engine. The bulb looks like the ones on the miniture outside icicle lights except it is
12V instead of 120V. Hope this helps.
The 8702 is a 4-6-4 Hudson form 1977-78. That would place it in the 1-9 MPC era supplements. Ont the page it is number 3-31 and 3-32. Acrobat will list it as page 140 in the header. You may want to print the two pages. The motor breakdown is page 418,and 419, 15-69, 15-70