Hello everyone!

Please forgive my complete and total ignorance, but the saddle on my 78 Motobecane GT mixte (the original Selle Royal that came with it) has a nasty gash in it and I would like to replace it. All I hear about old French bikes is "French bikes! Hard to repair! Different threading on everything! Different parts!" My question is: can I buy any old saddle or will I run into compatibility problems? Like I said, the saddle and the seatpost appear to be original to the bike. And then, once I have a new saddle: how do I actually swap them out? It is easy enough for someone who isn't at all handy to manage? (If this is a question better suited for C&V, let me know, too!)

Thanks!