It's been awhile since I used a maintenance set also but I believe it's your spre code plus 91. Then you type out LD on the keypad (I think it's 53) for load, # for a space, then your load number such as 36, then ## for enter. If you're testing trunks You would type out TRK on the key pad, etc.
I'm pulling this from memory though so I might be off a bit. But that's the jist of it.
Hope this helps and I hope I'm right. Good luck!