Welcome! I'd say it's worth fixing it up. There's a very pretty machine with some family history for you hiding under the grime. As suggested, spend some time reading here before you start, sewing machine oil is your best friend when it comes to cleaning these old machines. Anything harsher stands a good chance of destroying your decals.
I thought the thing hanging off the machine was a dead mouse too until I looked closer. Be happy it's a thick pincushion, a lot of machines just had an old cloth wrapped around them there and over the years the pins scratched the finish off behind them.
Rodney