Hey Lachlan,
I currently own a 2009 toyota corolla hatch!!
Trust me man u wont regret it.. I bough tmine as a demo car and i loved it the first day i sat in it. and i still love it now 1 and a half years later.
I'm not too sure what to say about your lights but what i can tell you is that the stereos are easy as to fit in... If u buy a genuine toyota stereo from another corolla. then its easy .. you just pop off a few of the interior parts arouns the stereo then unscrew 4 screws just like u have been told... comes straight out..
the only thing that u may have to look out for is that some of the stereos need diffewrent wires... depending on what u want..
When i bough tmy corolla i have just the standard ascent stereo in it but i have since then upgraded it with a genuine touch screen one that comes in the brand new corollas of today...
I didnt need any new wires to start out with but the best thing about these stereos is they have plug and play reverse cameras and everything so if u went down that track they plug straight into the stereo.
Performance wise..
It can be hard to make a modern day car go faster but the corollas are interesting...
K and N filters are definetly probably ur best option... I am actually currently working on putting one on my car now aswell.
If you know what your looking at under your bonnet u may be interested at looking at your intake.. If u folow it it comes out of the air filter and down into the front bumper but then curls around and goes straight back up into the engine bay and it is basically sucking in hot air....
I did a little bit of customization myself which i will upload some photos for you in two seconds... but all i did was got rid of some of the mounts that held the intake in place and i curled it right underneath so now it is sitting just in my grill....
It is like a forced cold air induction now its really cool. the only problem that i believe i will encotuner is that the air i will be inducting will be dirtier so i may need to change my filters a little more often then i usually would..
When it comes to speakers the corolla is a small car and so the stock ones seem to do the job but if u actually research it the stock ones are terrible....
If u take them out and actually look at the magnets u might even think to yourself .. " how do these things even make noise?" lol
but in saying that i have big plans for my audio because i really want a complete alpine system through and through... will be a lot of money but it will sounds really nice once I'm finished with it.