Are there any community patches or mods for the gamebreaking and questbreaking bugs or other bugs? I'm a little scared of playing for hours only to get screwed by bugs having read online about the game having so many.

http://witcher.wikia.com/wiki/Bugs

No, afaik there isn't a big community patch. Though there are some fixes for bugs, when they actually happen.
A user created an unofficial patch 1.5.1, which mostly contains dialog fixes.
http://www.gog.com/forum/the_witcher/mod_unofficial_patch_1_5_1/post1

But there are some good mods for the game out there (I especially appreciated a higher difficulty, although it was quite hard in the beginning):
http://www.moddb.com/games/the-witcher/mods
http://www.nexusmods.com/witcher/mods/

Well, I can tell you this: I played the game about two years ago and managed to make it all the way through without much trouble. Since then I bought a new, more powerful GPU (switched from Nvidia to Radeon HD). I tried playing the game again a couple weeks ago, and this time I'd get a third of the way or halfway through and the crashing would make it impossible to continue. I restated three times and tried lots of different fixes, but finally I gave up.

The game is riddled with bugs that could potentially destroy your ability to finish it. On the other hand, you could finish the whole thing without much trouble. It's tough to say what will happen unless you try.