Brew build fails, how to fix brew these doctor-reported problems?

Question

I wish I was programming, but I'm admin-ing instead. I want to install imagemagick with brew, but it fails to build. 1) brew doctor says:

Warning: "config" scripts exist outside your system or Homebrew directories.
`./configure` scripts often look for *-config scripts to determine if
software packages are installed, and what additional flags to use when
compiling and linking.

Having additional scripts in your path can confuse software installed via
Homebrew if the config script overrides a system or Homebrew provided
script of the same name. We found the following "config" scripts:

  /opt/local/bin/freetype-config
  /opt/local/bin/gpg-error-config
  /opt/local/bin/ksba-config
  /opt/local/bin/libgcrypt-config
  /opt/local/bin/libpng-config
  /opt/local/bin/libpng16-config
  /opt/local/bin/Magick++-config
  /opt/local/bin/Magick-config
  /opt/local/bin/MagickCore-config
  /opt/local/bin/MagickWand-config
  /opt/local/bin/ncurses6-config
  /opt/local/bin/ncursesw6-config
  /opt/local/bin/pcre-config
  /opt/local/bin/pkg-config
  /opt/local/bin/python2.6-config
  /opt/local/bin/python2.7-config
  /opt/local/bin/Wand-config
  /opt/local/bin/xml2-config

Some of those look like they're related to imagemagick. Did my failed install do that? This info is helpful for diagnosis, but what should I do about it?

2) It also warns:

Warning: You have MacPorts or Fink installed:
  /opt/local/bin/port

This can cause trouble. You don't have to uninstall them, but you may want to
temporarily move them out of the way, e.g.

  sudo mv /opt/local ~/macports

I can do that, but is it a permanent problem that macports is in my way, and I have to move it then move it back each time I use brew? Can I setup somehow so brew and macports don't interfere with one another?

3) Maybe this is a symptom of the same problem, but I also get:

Warning: Unbrewed header files were found in /usr/local/include.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected header files:
  /usr/local/include/node/android-ifaddrs.h
  /usr/local/include/node/ares.h
  /usr/local/include/node/ares_build.h
  /usr/local/include/node/ares_rules.h
  /usr/local/include/node/ares_version.h
  // ... about 80 of these, all beginning with /usr/local/include/node

This answer blithely suggests that I "Remove them and install nodejs from homebrew". Just rm-ing these files sounds wrong and dangerous. Is that the right action, and can someone suggest a safe procedure to replace a port installed nodejs with a brew installed one?