how to change gearshift solenoid on automatic 98 jetta??

Hi there!
The old solenoide in the gear shift was getting stuck on parking (only on cold weather)...so I bought the new one. However I can't get to it. I noticed that it has a couple of screws facing downward on the bottom of the solenoide, but there's no room enough to get any kind of wrench to loosen such screws. The entire shift is encased in a metal box which is not removable..
Please help me ...what should I do?

98 gl jetta