RPM and steering wheel problem

Dear Sir,

2006 Honda civic fd1 automatic transmission.

i put brand new 2 front lower arm bushes on my civic. now i feel steering wheel become more stiffer than before.

wht is the problem with it..?
another problem, when i park the car (engine idle) or when driving,i can see RMP go up and down little some times.
do i need to change the spark plugs..?

pls let me know.

Thanks,
sampath