There are two official patches you should look for:
1) il2upgrade_1.1a.exe
2) il2upgrade_1.2.exe
Try this link.
Install both patches, in sequential order of course. After you are up to version 1.2 you can then add the optional 1.2ov patch, but this patch is only for if you want to add custom speech packs like
BBQ's English Voices. DON'T substitute 1.2ov for 1.2, and DON'T skip the 1.1a patch!
Mission4Today is one of the few sites left that has any downloads for the original IL-2 game, and even so you have to know what you're looking for because 99% of what is in their library is for Forgotten Battles and beyond.
Start here for campaigns and/or the game patches. There really isn't any point in looking for repaints unless you are flying online, as you can't use custom skins in the single player mode.
I have a sizeable collection of original IL-2 Sturmovik addons archived on a backup disc, including campaigns that may not be available at Mission4Today. If you are looking for something in particular I may be able to provide it to you via e-mail.