Help needed to install IQaudIO's rotary encoder in piCorePlayer

Hi all you Pi/Linux experts out there.

I have build a SB Touch replacement using a Smart Pi Case, 7-inch display and an IQaudIO Pi-DigiAMP+ board.
I just need to make the rotary encoder functional. It is the £5 one bought from IQaudIO.
I have read just about ALL I could find about this subject in the last few evenings but unfortunately still without luck.
I'm kind of a Linux NOOB so I need a little help here since there aren't much easy information available out there.

It seems I need to either find a IQ-rot binary with the cardname changed to "IQaudIODAC" or compile one myself. Is this correctly understood?

I also disabled the "audio=on" line in the config.txt file to remove the internal soundcard. Is this correct? Information about this is somewhat vague.

I have come this far in my attemt to compile the modified IQ-rot.c file:
Installed these libraries: ipv6-4.9.50-pvpAudioCore_v7.tcz, git.tcz and compiletc.tcz

Now running the compile command "gcc IQ_rot.c -oIQ_rot -lwiringPi -lasound" fails with an error about it cannot find the wiringPi.h file.
"wiringpi" is installed and running but the wiringPi.h file doesn't seems to be present on the SD-Card. Copying the wiringPi package in and changing the path to the wiringPi.h file also doesn't seems to work. Or should the wiringPi.h file be placed in the same path as the running wiringpi?

I think I'm almost there but if somebody have a few minutes to help me here, I would really appreciate it :-)

Many thanks....

/Martin Roerup