Your post would be better in the "Newbie Board" but a short answer anyway.
No and no. No it must not be in the boot.bin and no, there are no specific tools to open a boot.bin.
Every game is different and each game is normally unique on the form it is build.
The rules to find/modify/reinsert your text are basically all the same for each system so if u want to hack, go read one of the many SNES/PSX/NES/etc... beginners guide out there but u will spend the most of your time in front of an screen like this:


and if u are lucky that u have an disassembler for the PSP, spend some more time in front of a screen like this:


and the rest probably with screens like this:


Sorry if it sound a bit depressing but translations is not like translate a word document.
The most of the time u will spend it trying to figure out where the text is, in what language it is and how to open it so that u can read it. Then spend alot of time to get it back inside the game again and make the game understand what u translated. The translation of the text itself it's probably the easiest part.

Just to be curious anyway....what game u had in mind to translate??

Yeah EBOOT.BIN usually contains some game text (but not always). Also remember that you have to decrypt it first. CPK files are usually partially compressed, luckily UTF_tab can decompress and extract files out of it. Are you sure there weren't any useful files extracted from the CPK? PSP games commonly use Shift-Jis, UTF8, and UTF16LE encoding for text. Be sure to check the files for each encoding, one game that I worked on used all three in the same file!