i have a 02 MCS and have been loosing electrical items for some time

1st the htr. system will only blow in neutral position
2nd seat belt lt. is allways on , even when key is out of car .
3rd air-bag lt. on
4th nav. system only shows start screen
5th clutch switch stopped working ( had to jumper it to start )
6th radio shows disabled

so question is how to test this
is the gateway mod. interchangeable with other same year model's or are they only for the car they come with ?

i have had trouble with a leak on the rt. front A-pillar so the gateway has got wet