LOL Come on, give a guy a break!

What I said a few weeks ago was "When used properly, an 8 ohm tweeter and an 8 ohm woofer separated by a crossover will appear as a uniform 8 ohm load to your amplifier so your total impedance will remain unaffected."

There'* a crossover on that tweeter, so by all means try it. Just parallel it with the full range speaker in the door. I promise you won't blow your head unit.

But you'll get mightily better sound with an aftermarket 2-way component set, because that factory full range in your door is basically junk. Adding a tweeter can only improve things, so HAVE AT IT!

Update......

Since you guys are back at it..... i put the other side in and it has been playing fine for a week. Nice little improvement for a few bucks. I had been fairly confident about the imp load when i didn't hear any SPL difference when i had ony updated the one side.
Notes:
-The door removal info is good, just be real careful in the last step with the black strip at the top. Very slowly off starting from the back moving to the front.
-Figure a way to get the "tweeter" into the panel BEFORE you rehang the panel. It'* a real biyatch to torque that sucker tight. The issue came upon me because the lead clip was right next to the 5 1/4. the splice had to go on the lead ( not very long either) to the door. It was easiest to set up the splice, mount the tweeter, mount the panel, and then do the quick splice.
-On CD there is a "glare" in the upper midrange and top end where the two speakers overlap. The EQ handles it just fine.
-Got fed up with the stereo image about mid dash. Traced the speaker surrounds onto a thick computer mouse pad and then cut them out. Then beveled them. About 3/8" on one end, and almost nothing on the other end of the circle. Remounted the speakers with the pads which made them point a few degrees up. I like that, it raises the soundstage up onto the dashboard. FWIW. I'll probably do it when I get componenets.
-Baffle behind the speakers. Crappy padding or something is just fine. I thought it cured some vibration i heard.... real or imagined.

PS Swapped in a new driver side power mirror while I was at it. You have to undo the middle frame of the door that has all the window power crap on it to get to those impossible positied bolts. Hint: don't worry about the lower window guide falling off, it goes right back into place when you rebolt it.