Mono amps are more for subwoofers. They have a higher/better Wattage output per the one channel.
2+ channel amps are "COMMONLY" more used to power mids/highs speakers/subs.
If you take it to a local audio shop, they normally charge anywhere from 60-150, depending how easy/hard it is.
Installs are VERY easy.
Run the power wire through the firewall/floorboard on whatever side the battery is, all the way to the trunk (hide it under panels etc.)
Run the remote wire down the OTHER side of the power wire (power wire driver side, remote wire passenger side.)
Find a good spot for your ground wire, normally a bolt in the trunk connected to the body, pull carpet up to see them normally. (use sandpaper to grind away paint so it has a clear metal/wire connection. The shorter the wire, the better.. But give yourself a little room to play with it.)
Run the speaker wire from amp to the sub. Run the rest of the wires (
ground wire before power!!!)
If you need help, just ask here

Subwoofer is GG with anything/everything speaker related.
Also, many others here are very educated on it.
If you need detailed help, you can always take pictures of your setup/car/speakers and ask for advice that way... Where it should be ran, where to set it up.