radiometric dating vs. fundamentalist preacher

[No_Foolin'?]

The vast majority of my "book" knowledge is in the social sciences, so I know precious little about anything having to do with the physical sciences.

So I need some help, because I'm in over my head here with a local preacher who believes the bible to be the inerrant word of God. He has much to say about the natural sciences (e.g. regarding evolution, the origin of the universe, etc.)
and among his arguments is that the earth is literally somewhere in the neighborhood of 7,000 years old.

Seems his main reason for believing this is that the bible says so, or at least this is his interpretation of what the bible says.

Anyways, the cornerstone of his argument against the sciences is what he sees as the unreliability of the methods used to date things, such as the fossil record for instance. Specifically, this preacher questions the validity of the results obtainined using both carbon-14 dating or radiometric dating.

From what I understand, these are the two principal methods that scientists use in their work.

My layman's assumption here is "How possibly can all of this scientific understanding that we (think?) we have rest on such faulty ground? Surely my friend is wrong about carbon-14 dating and radiometric dating". No?

How reliable are these methods? And if they're so unreliable, how can reasonable, thoughtful, and serious researchers trust the validity of their findings / theories?

Are we to accept their theories - take evolution, for example - only with a large dose of skepticism?