It'll propbably hurt - brief sharp pain that's not all that quick as it involves a very tight clamping process before you even get to the needle, but you'll cope [I did, though a friend who had one nipple done while I had both of mine pierced, turned pale and had to sit down sucking on sweets till he pulled himself back together].
Be very selective about where you get it done. You could look on some actual gay websites in your area, or in gay newspapers which are often free in major cities, as the better places often advertise to the gay community, though [and I do not mean to offend you] from the pretty offensive way you use the word "gay" I suspect you would be a bit uptight about going down that path. Still you could ask around people you know who have had piercings done where you live. Make sure it's a properly licensed place and that the staff are friendly and can intelligently, and patiently if necessary, answer your questions. The placing of the piercing is critical and will depend on your nipple size, how your nipple sits on its aureola and the skill of the piercer. make sure he or she has practised on lots of other people before you.
Penis piercings also hurt despite what some people reckon, and I was surprised at how much I bled afterwards. I subsequently learned that some people bleed very badly after a Prince Albert [which is what I had] and I even know of one guy who lost so much blood he had to be hospitalised. So it's important to dress the wound well and to be able to apply sufficient pressure without cutting off the circulation to your penis. A good piercing place will tell you all that you'll need to know.
There are some good websites - both medical and commercial - that deal with various aspects of piercing, possible side effects, cautions and so on. If you have your immunizations up to date [especially hepatitus B - a very rare complication but why risk it at all], and you are clear that you know what to do to maintain rigorous hygeine throughout the healing periods, then you should be fine.
Now that I've done it I am happy with it but I can tell you there are times I'd rather my nipples and dick were just the way they were before I started. It's a bit like a tatoo. Sure you can get rid of them but once you've made the effort you kind of get hooked and I have even increased the guages of my piercings. I like the hefty weight of my Prince Albert and I think my nipples look great though other people can get a bit strange about them - which is not an effect I particularly wanted to have to deal with.
While your current partner might be turned on or might be prepared to let you enjoy having piercings, there may be others for whom it will be a real turn off. Finally it's got to be something that you do because it's how you want to see yourself - like your general grooming, how you look after your physique - or not - and if you really like it chances are your partner/s will too.
Good luck!
