I love your story! So happy that you have your grandfather's machine. You can clean the machine yourself, just follow the tutorials on cleaning from MUV. I just clean my machine's with sewing machine oil only to protect those decals.
The belt is easy to put on and tutorials can be found on you tube. Instead of the metal clip to attach the leather belt, I use dental floss to hold it together, just sew through the two holes and finish off with a half-hitch knot.
Are you going to name your machine after him?
Please post your first project that you make using this machine at quilts made using vintage machines. I love seeing folks' projects.
Thanks for sharing and Enjoy!