Question: I'm a complete Ada newbie, though I've used Pascal for 2-3 years during HS.

IIRC, it is possible to call Pascal compiled functions from C/C++. Is it possible to call procedures & functions written in Ada from C++?

Answer: 
That kind of thing is done all the time. The trick is to tell both sides to use a "C"-style calling protocol for the routine. In C++ this is done with extern "C" declarations, and in the Ada side with pragma Export ("C", ...

Look those up in your favorite respective reference sources for details. Watch out for pointer and reference paramters!
Yes. Several years ago I wrote a short simple demo to prove it. There were two DLLs, one written in C++ and the other in Ada. They just added constants to floating point values. Two apps, one in C++ and one in Ada, each used both the DLL. So every possible combination of C++ calling/called from Ada existed. It all worked fine. This was on Windows whatever version was current at the time; I don't recall but may have gotten this working on Linux or BeOS.

Now if only I could find the source code from that...