Lots of people have done it and there is lots of information on how to do it right on various boating forums. It's a topic that has been discussed in detail many times on the GB owners forum
grandbanksowners.com/ You may have to join the forum to access the archives but joining is free. Several people on the GB forum have done this and replaced the original teak with several options, from a fiberglass, painted non-skid surface to artificial "teak" surfaces, to re-teaking.
Done properly it's a big job and if you hire it out, can be very expensive. It is certainly possible to do it yourself if you have the time, tools, and willingness to learn to do it right. If the teak is to be replaced by a fiberglass non-skid deck it usually requires additional layers of glass be put down over the subdeck after the teak has been stripped off and the subdeck surface prepared. The reason is that the teak adds stiffness (not necessarily strength which is not the same thing), and that stiffness should be restored after the teak is gone. Two layers of glass matte and resin over the subdeck tends to be the typical application.
Depending on the actual condition of your deck, it is also possible to overhaul the teak deck. This subject, too, is discussed many times and in great detail on the GB forum. We did this on our own boat and its now-39-year-old teak deck is still going strong although it has been oversanded by previous owners and needed a lot of work when we bought the boat.* We treat it well and take care of it properly these days, because if we let it deteriorate again I doubt it could be brought back again.
A fellow on our dock replaced the teak deck on his Island Gypsy with a fiberglass deck over the subdeck and a painted-on non-skid surface. The end result looks better than if the factory did it and the deck is so strong you could probably land a plane on it. He did all the work himself, got the advice of several shipwrights before he started, and it took him one and a half summers of almost daily work to complete the job. When I complimented him on how good it looked he said that had he known how much work was going to be involved in doing it--- and he did it correctly: there are lots of "quick fixes" you can do that will eventually fail--- he said he never would have attempted the project.
Like everything else in boating, you can do it very poorly, you can do it perfectly, or you can do it somewhere in between. This guy, according to some shipwright and marine engineer acquaintances I've talked to who are familar with or helped him with the project, did it perfectly.* And as such, it probably added a fair amount of value to his particular boat.
*
-- Edited by Marin on Monday 20th of February 2012 07:23:52 PM