if you can get a pieced together quality vintage bike with Shimano or Campagnolo(campy) components built by an actually bike tech for 400 bucks in good condition, don't fucking hesitate.
have you ever used newer shifters? they're incredibly easy and smooth to use.
Road Shifters:
https://www.youtube.com/watch?v=6YYzVjWDJy0
Mountain Shifters:
https://www.youtube.com/watch?v=dil-Lyr3bPI