2000 DTS won't go out of park

Have a 2000 Cadi DTS and it won't go out of park unless I push the orange button under the dash by the center console. Thought we should check the cable and linkage first!!!  Dealer told us it could be the floor shifter selonoid which would cost about $400.00 and it's located somewhere under the dash and Murray's said it could be a auto/trans control selonoid that would be located on top the trans. Any advise you can give me. If it is the floor shifter selonoid how can I check it to see if it is faulty and what is involved in getting to it.
My understanding there is also a selonoid to do with the brake but the brake lights do work.
Thanks,
Bev

Spilled drinks on console/shifters cause 90% of there concerns. To see whats going on with shifter you will need remove trim panels on console, be carefull because they are expensive to replace. Cleaning shifter can be a tedious.