As the previous guys said: No problems, be sures. Just make sure you get the
IL-2 Sturmovik: 1946 Dvd-version.
It should cost around 15-20 euros. It's the only version you're going to want, since you only need one patch to make it current. Anything else is a real pain in the ass to bring up to date.
As for patches, 4.08m is the most current "stable" release, while 4.09b1m is the newest beta. You apply 4.08 straight on your 1946 installation, after which you apply 4.09b1m if you want to. Most online playing still uses 4.08m.
edit:
Patch 4.08m(scroll down a bit to find the download links)
http://www.pacific-fighters.com/en/home.php
Beta patch 4.09b1m
http://forum.1cpublishing.eu/showthread.php?t=2462