I've been using Sonar 7 for over a decade now (very familiar with it) and have also been using iZotope Ozone 3, particularly the compression and limiter for some tracks and the limiter for mastering. I know there are much better products out there, however I'm switching over to the new Sonar Platinum, particularly because I now require VST3 which the 7 version doesn't have.
 
I want to make this transition as simple as possible (I'm now a senior but seasoned songwriter). I note that the new Platinum comes with mastering tools. Would anyone recommend any of these for compressing and limiting for mastering that are as user friendly as my old Ozone 3 and if so, could you direct me to the manual for this plugin? No, I don't want to continue with Ozone 3, I'd prefer to learn something better since I'm making the transition anyway to Platinum.
 
Thanks for taking the time, it's appreciated!
 
 

Platinum will use VST2 formats without issue, but 32-bit VSTs can be problematic in 64-bit SONAR. What format is Ozone3?

I used Ozone 3 and though its been upgraded a lot since Ozone then its still a very viable mastering suite. I have Ozone 7 Advanced but I often use Ozone 4. Really, if you like what Ozone 3 does you don't need to upgrade except if you go 64 bits. The only reason it is not on my system now is I don't believe they offered a 64 bit version.
 
To answer the question Ozone 3 came in DX and later VST.

If you are using 32bit DX format plug-ins, they will only run in a 32bit version of SONAR. By default the Command Center installs 64bit SONAR on 64bit Windows. To install the 32bit version of Platinum using the Command Center make sure the "Verbose Install" option is enabled on the settings page. Click the gear in the upper right of the Command Center to open the settings page to set the "Verbose Install" option. Then reinstall, the 32/64bit option will be displayed along with the rest of the installer options. You might also consider staying with 32bit SONAR if you use a lot of old 32bit plug-ins. Hanging on to old plug-ins is not the best idea. They have not been updated in some time and can be a problem in newer OSes and DAWs.

hi Rubicon,
I would say yes.  Sonar Platinum has a good mastering multiband compressor and mastering linear EQ.
Both are very good (EQ does mid/side as well).  As far as being as easy as OZ3, I would say they have a relatively straightforward learning curve.  Another feature you might want to take advantage of is the new concrete limiter.  It'll come in handy as well.
Overall, my small suggestion would be to take some time and digest as much of Sonar Platinum as possible.
This is going to be a bit of an undertaking since you're coming from Sonar 7.  There's a lot of new writing/mixing and mastering features that have been improved, reworked and overhauled.  You'll love it in the long run, but you gotta get there.

Ozone 3 has one cool feature that even subsequent versions of Ozone don't have, and that's a rather rough-edged exciter. Starting with O4 and beyond, the exciter got more genteel. I miss O3's exciter.
 
The good news is that Ozone 3 should still work just fine, even in 64-bit SONAR. (Although I can't test it because O3 sadly went away when my DAW got stolen.)
 
And more good news: as a previous iZotope customer, they'll let you upgrade to Ozone 7 at a substantial discount. The Music Production Bundle has been on sale a couple of times (don't know if it still is) for a crazy low price. 
 
An upgrade will get you more cool features than one can count. If you go with Ozone Advanced, you get separate plugins for each of Ozone's modules. Everything you love about Ozone 3 will still be there, plus much, much more.