Hello Dave, Frank Here.
I felt like you about taking the rifle apart. I found this, the pictures speak for themselfs:
http://www.network54.com/Forum/184474/message/1227047934/Diana+48-52++T01+trigger+disassembly-assembly++(picture+warning)
You have to have a compressor as the spring is very strong. The trigger module will come right out. The spring will push it out.
Take it apart carefully and that the small springs don't go flying. I worked on a large towel and laid everything out in order. More than likely a spring will fly either while taking it apart or putting it back together so work in a surrounding that will make it easy to find the spring.
A note about putting it back together: Getting the two holding pins installed looks easy, but I saw the safety has an arm part that can get in way of the pins. Through the front hole I held up the arm and put the rear pin in first while moving the safety and lightly tapping on the pin. After you get that one in, the front pin is clear to be installed... You have to be very careful and not be forceful as you would bend the safety arm. If it don't go easy there is something in the way. What I did was put a slight taper on one end of the pins the to help them slide past the arm. As you can see there is an upper straight part and a lower bent part so you have to watch for both and not be touching either when putting in the pins.
Hope this helps and if anything further just contact me..
Frank