hello, i am new to PSP softmodding but have had a lot of experience with modding Xbox.

i have a "fat" psp (the old big one, not the new slim), a very early model i think. i have been updated it (before i thought about modding) and i dont know what firmware version i have, and i want to mod it. i have a few questions (btw i read some of the FAQs)

1) how do you check the version of your PSP FirmWare?
2) what version of homebrew firmware should i install (is M33 the best?)
3) how do i install it?? do i have to downgrade or something??
4)will installing a custom FW affect regular UMD games? can i still play them? can i play them online? can i switch between firmwares?
how do i do these things?? please, ive read some things but cant find an answer, and i kind of need a more directed answer.
edit- alright, i found out my FW, its 3.90