Pretty much any collision at near c would be like cosmic rays. Cosmic rays, without shielding will destroy small things (like DNA) but have little to no macroscopic effects on material. Increase the size of those cosmic rays from sub-atomic particles... And you need shielding or your ship gets ripped apart. However, space is such a vaccuum in all but a few places that during interstellar travel, you would likely encounter only a couple of incidents in which shielding to protect the hull would be necessary. For the most part it would be the same as cosmic rays. Between two stars, assuming there is no star between them, the only likely place to encounter debris capable of doing damage would be within the stars' immediate vicinity. The rest would be pretty much clouds of ionized gas/plasma... cosmic radiation. By the time you were within any danger of a strike you would have already begun slowing down the craft to orbital velocity of the target planet.
As for FTL travel, to my knowledge we do not have any working mechanisms/theories which could make it work. And if it is "within 100 years" that is the technical way of saying "I have no freeking idea if how to do it or if we ever will, but if we do, based on the speed of techtechnological advance it can't be to far off." Basicly the same as my answer. You can bet the same month as FTL is found to be possible, every news and especially science magazine will have that on the front page, followed by several months of follow up articles. Heck, metamaterials (possibility of invisibility) have had several, and that is not nearly as important and world shattering a discovery as FTL travel would be.
And off my brain goes on another tangent... An interesing thing about FTL travel is if we manage to colonize other worlds hundreds of lightyears away, it would be possible for one's grandchildren to one day pull out a telescope (a rather big one...) and watch the maiden voyage of their grandfather's ship as it embarked from earth a hundred years before...