Owning a 3rd gen for the past decade, I can tell you a lot (but be forewarned, mine is a spyder...)
1: 210k miles, and I have never had to crack the engine open. (changed the timing belt, water pump etc.. but never had to take the head off... I should though, the blow by in extreme nowadays. I should replace my oil cap with a muffler)
2: yes...ish. it will be TIGHT. you could put it in, but the front seat might need to lean forward... and have fun getting the kid in it.
3 common issues:
3a: ricers touching them. idiot kids think they can get power through all kinds of idiotic mods that make them worse.
3b: timing belt, timing belt, timing belt. many NEVER get the recommended timing belt change, and if it snaps, you have boat anchor (interference engine)
3c: maintnenence in general. kids buy them, and instead of keeping them maintained, they drive them like idiots, then sell them.
4: In the RS and GS the engine is a 4g64. a 2.4l SOHC. "the" 4g63t (from the 1g and 2g eclipses) does not swap in (wrong direction). BUT the evo8 4g63t swap right in. the REAL modders, put the hyundai 2.0t head on (or the evo 8 head) and turbo and have a 2.4l DOHC turbo car. the bottom end can't take a lot of boost though.. and 12 psi is on the edge.
4a: if you get a GT/GTS you have the 6g72, that you can swap in a 6g74 or 6g75 CHEAP for good power (4cyl to 6cyl, or vice versa involves tranny, and subframe changes, so they are kinda silly)
other side info:
on the highway, the gt gets mileage than the 4cyl.
intakes and exhuast do NOTHING because the OEM parts are HUGE.
the aftermarket SUCKS. you can only really get no-name crap that looks cool, but lowers functionality... or you are going to pay out the nose.
any questions, talk to me... I KNOW this stupid fat pigs.. like the back of my hand.. I have autocrossed them, and before that it was a looker... I have a love/hate relationship with this beast... partially because it REFUSES to die.