Engine Installation

Sir, I have installed Rotax 914F on Stemme S6 aircraft, I have to change the engine installed on aircraft, I arranged a used overhauled engine from one of my friend,

I am confused about changing of TCU and engine hours counter with new engine, in aircraft  Hobs hour meter shows 380 hrs and new engine is 260 hurs used and repaired from rotax,

Is it compulsory to change Tcu and eng hour counter with every engine change , If not then how to configured new engine with old TCU and engine hours counter, 

More over there is no information about used engine change in installation manual.

Regards, khan