You don't have to remove the bumper to get at the last headlight screw. Just take out the screw that connects the bumper to the fender in the wheel well. Then you can pull the bumper down a but to get at that last screw. Note: might not work with a fiberglass bumper.
Here's how you can seal the headlight without putting them in the oven. I removed my headlight to actually do it (did all the way around) but just threw tape on to illustrate what I meant...https://www.celicahobby.com/ubbthrea...#Post1953313005
If you want to paint your headlights, you have to open them first...
There are really good directions for opening the headlight here. Do steps 1 through 5, but not 6 and beyond. Steps 6 and beyond are for the different inserts, no need to trim anything for what we need.https://www.celicahobby.com/ubb...apsed_2__1.html
2 things. I left the lights in for a full 15 minutes (preheat oven and turn it off right as you put in the light) and then I had my kid help me, he opened the clips on the lights as I pulled it open. I only had to heat each light once, and opened them with one complete pull. Good luck, they look awesome when they're done. I used Duplicolor wheel & rim paint. The color for the paint in canada is Graphite, so it might be different in the USA.
Here's a guide I made up when I did mine.http://celicagarage.com/forums/viewtopic.php?t=1185