My guy had to get dentures at a relatively young age. The first thing you need to do is look at all of your options. Dentures are not the only option. If you have enough teeth that are well supported, you may just need partials that clip over your good teeth. If you can afford it, you can get implants that look just like your natural teeth.
But, for they great number of us that can't afford the surgical options, dentures will have to do. In general, as long as there isn't a lot of abscessing, having your teeth pulled isn't very painful because the nerve is pulled out with the tooth. Your dentist/oral surgeon will probably put some stiches in where the teeth were pulled. Then you have to take very good care of your gums until they heal. Dentures that properly fited are usually not painful. That's why it's important to have the work done by someone reputable. The biggest problem with dentures are sore spots cause by your gums shrinking are hard things getting under the denture. That's why you have to keep your dentures clean and rinse them off every so often.
As gaps develop, you use various denture products to fill in so they will fit comfortably.
I can't not emphasize enough how important it is to get good quality dentures and a good warranty. A friend of mine thought she'd save money and ended up have the fall out her dentures. It got so bad, she started Super Gluing them back in.
Remember that you dentures will be with you most of the rest of your life. Far longer than a new car. Make sure that you get exactly what you need and don't let a shyster dentist talk you in to buying cheap crap.