We are a 62 year old married couple planning a holiday to see Costa Rica. CAn anyone give us suggestions as to if we can do this as a self-guided tour, or is it advisable to take a guided holiday?

Yes you can do it on your own, it would be good to learn some spanish if you can. You can take buses to different places in the country and that's cheap. You could go to Tortuguero, where you can see turtles coming to nest at the beach at night, but you have to hire a guide for the night to do that ($15 per person is the best price you will get). You could also rent kayaks and go kayaking in the National Park, that is really great, just pay good attention to where you are going or you will get lost (that happened to me). You can also pay for a tour of the canals by boat but kayaking is really ten times better. You can see tons of animals. In tortuguero, stay at "Tortuga Lodge," its really good but I'm not sure how much it costs. You should definitively do a self guided trip, you will learn a lot more and have more fun. The people here are nice and helpful but be careful too, tourists tend to let themselves become easy targets. Good luck.