well, first off I would update to 4.1E or 4.2E if i were u, but u can stay on 3.2 if u prefer, but there isn't any benefit to being on 3.2 anymore (not since newer firmwares have been pwned)
do u have bootmii as boot2? if so, u don't NEED to install priiloader as u already have the best brick protection, if u only have bootmii as IOS then u should definitely install priiloader. But even if u have bootmii as boot2 u can install priiloader for its other functions (see #4)
no priiloader does not hurt compatibility with any HB apps.
2) uninstall priiloader (see #3), but i doubt u'll have problems like this
3) just launch the priiloader installer again, and this time hold b and press minus (or just press minus to use IOS36 to uninstall instead of IOS249). Another way to uninstall priiloader is to reinstall your system menu and use nand clean. And the last way is to restore a nand backup from before u had priiloader installed.
4) brick protection, system menu hacks (like regionfree everything, block updates, etc.), boot settings (u can set your wii to boot to usbloader directly, or to a crazy intro video, or to HBC, or to bootmii, or to priiloader, or u can let it continue booting to the system menu), there is a setting to make your wii ignore the turn off to idle setting (so your wii will always turn off to red instead of to yellow, unless you turn off the wii from within a homebrew app).
5) the latest
released version as of now is priiloader v0.3b, it should say this in the meta.xml (or the HBC description of the installer), and it will also say the version on the first screen after launching the installer
seriously, just install the thing