I have been slowly delving into reaktor over the past year or so and I am finding a ton of great resources here. adsrsounds.com
Also, I am reading Designing Sound by Andy Farnell. It is using Pure Data, but a lot of the same principles apply.
There are some good basics on youtube if I remember correctly.
The big thing really is remembering there are two types of data, numbers and audio stream. If you want to use audio to say... change the frequency of a filter you have to put a converter between the two.
Other than that if you know the principles of cv and gate (cv being pitch, gate being on....
In many cases OSC is used to encapsulate MIDI messages into UDP packets so they can be sent over a network (sometimes to multiple destinations).
However, the OSC protocol allows many more types of data to be transmitted. For example, you can send 32 bit numbers (float or integer) compared to 8 bit integers in MIDI, and symbolic messages, too.
Reaktor macros are implemented graphically and not programmatically as in via text. You would need to identify some sort of macro block that allows the text transform you are suggesting then route the result to a parameter pin.