Explaining how difficult or easy something like this depends on you and your mechanic skills. Obviously, but that's the answer and I have no idea of your mech skills.
I took off my OEM header in less than 7 minutes. It's eight 12mm nuts and one large bolt in back above bread-box. The slip-on is couple bolts (I didn't have a slip-on). Putting the Delkevic header on is more similar to how the OEM goes back than say, the Akrapovic I have. The Delkevic secures the primary pipes the same way as OEM, the Akra uses individual cups with spring retainers on each primary (to head). Once all 4 primaries are finger tight, gather them to the collector to slip in. Some may have better luck joining the primaries to collector first...at end of day, do what works for you.
Remove the one 10mm bolt in bottom/middle of radiator to gain a little more room.
Remove bottom plastic panels.
When removing O2 sensor, be VERY careful with the tip. You can easily damage them (unless reflashing ecu).
When putting O2 sensor back in new header, pre-wind up the wire so you don't kink it when installed (unless reflashing ecu).
Wipe down the new header with acetone (or 91% alcohol) just before starting (after all installed).
Install all bolts finger tight till all together. Then tighten as a unit.
ps. You got this!!