it can be done, the front circiut board of the faceplate can be cut off & the only traces that are lost are for the cassette itself, so no problem there.
then to have depth there like to install a single din head unit you'll have to remove the cassette portion of the headunit, but it's not just made to be removed. you'll have to take the head unit apart & you'll have to cut part of the outer tin housing too that extends down. the electronics can just unplug & be discarded. it's a little involved but not extremely difficult either really...
one minor issue is first time you reconnect the power, the head unit will power up & say "cassette error" on the screen, it'll also beep for about 5 seconds. once you press cd or am/fm or whatever it'll work fine & you won't see that cassette error screen again till you disconnect the battery or unplug the radio again, BUT the 5 second beep will still happen each time you start the car... it's a little anoying but I kinda got used to it for now... the beeper speaker is tiny & on the faceplate, could be disconnected but then it'll never beep for other stuff like tpms or whatever else it beeps for...