The first thing is to be a single person, or have a large enough house to get out of earshot of your partner. otherwise severe strains will develop in your relationship, during the first few months of your attempts. Other than that, go for it. You have a lifetime of pleasure ahead of you. Get a cheap fiddle(£100 or equivalent will be fine), decide what you style you fancy, buy the book or the video, or ask around for a teacher near you, and you're off.
    There is one possibly big problem, which you will soon find out, if you don't know already. You need a fairly good ear to play fiddle. With the guitar, you can get away with it, also keyboards, accordions, bodhrans etc. With the fiddle there's no protection, there are no frets to keep you in tune. If you can't keep it in tune(and a cerftain percentage of people can't) you'll have to give up, but there are plenty of other instruments to have fun with.
    Do persevere, you are about to start a relationship with the greatest instrument in the world.