Go bilstein and never look back
most of the time the 5000's or any other shock of the same type are too stiff for most applications except larger vehicles. You will have more comfort and performance with monotube shocks.
your gonna have to pull or drop the headliner in enough to put the drain line back on and use a worm type hose clamp to ensure that it stays put. Just did that to my camry for the same problem.
that is a check engine light. Go to autozone and find out what code the ecu is throwing, when the light is on. Sounds like a sensor that is starting to fail.
just being realistic, you can't have your cake and eat it too. if your that worried about offroading and pinstripes you might as well put a set of curb feelers on your runner to keep the curb from scratching your rims.
my tacoma was expensive, it has its fair share of on trail customization. Most cases a tree branch will grab the leading edge of the magnet and just take it off while leaving a good deep scratch.
I have installed them on a tacoma, you won't regret spending the money, but it sounds like you haven't done enough homework yet. Search around, this has been beat to death.
If you can manage it, get it scanned while the CEL is illuminated. Something doesn't jive with the truck when it's cold or whenever the light comes on, but when the criteria is met the light goes out. Sounds like something is partially failing or has lost some of it's metering spectrum. A CEL...
yes replace what you can at this stage. Timing belt, water pump, cam and crank seals, drive belts, any loose/wobbly idler pulleys, rad hoses, thermostat, etc. If some of the hidden stuff fail, you have to undo all of it to change them.
pop the hood and listen for the squeaky belt and adjust the tension appropriately for that specific belt. Or it may be an idler pulley that's bearing is going south.