Ive just finished building haskell from source.
[Thanks to all the folks who've made this so easy]

1. What is the official way for ensuring that some command like
$ cabal install vector
goes into my new haskell and not the old?

2. If I modify PATH so that the new ghc is found before the system one, will not system-ly things break (when for example I mess around in the haskell sources and break it?)

[BTW I am on debian testing/gnome and I gather that an increasing amt of sysad stuff is being done in haskell. So I certainly do not want that I play around inside haskell sources and synaptic for example stops working :-) ]