New stringers how hard is it?

How hard would it be to put four new stringers in my boat? 80's Supra I have never done this and any feed back would be great from those of you who have done it. Also where would you go about finding new ones?

it took us all last summer, but the old stringers came out in handfuls so it had to be done. A local guy helped us out with everything from the wood, resin, fiberglass, just ask around. If you want to know more specifics just ask im sure ill be able to help, but it is very time consuming