well, as far as looking the same, i cut the old pods out, which are not a standard size, or circular IIRC (the tweter+ conections was a oval shap - maybe wrong though) so as for just dropping a new tweeter in, not sure. Also as for cutting the pods out of the door cards, makes no real difference when grilles are on, when removed, the only difference is you can see the metal work.
as far as the dash goes on mine, when it now looks just the same as i have replaced the tweeter grilles, as i have moved the tweeters.
Also, ive been very carefull not to do anything that will effect resale value 0 the only metal cut is for cabels, and any plastic trim i have cut, i will replace bofore selling. the lack of tweeters will be solved by putting some coaxil speakers in the doors, the only things bar the holes for cables that cannt be returned to original is the tweeters and sound deadening.
You could mount the tweeters on the surface of the a-pillars, this will be easy, with say double sided tape, and give good sound stage height.
But at the end of the day, it what you feel comfortable doing, and really it need you to have a look, IE remove the dash and see if it will fit ect. as i did that over a year ago, so my memory of it is sctechy!