i would like to replace rear subfram mounts on my 89 300se,can i just use an air chisel and take them out without dropping subframe and press them back in with a jack,thanks for any help

There is a special tool for this job. Without it the change-out procedure is very messy. I would get quote from an Indie to do this. The mounts are not expensive. With the tool the change-out is very quick.
I managed to find the tool on the great auction site for $ 200.00.

I changed mine on the 83 300sd without any expensive special tools. There are some great step by step write ups on the entire procedure right here on this website that will guide you through the process. Not only will you be able to change the subframe mounts but while you have the subframe down you can also change the trailing arm bushings. For those I used the $25.00 press tool from harbor frieght, or you can rent it from auto zone etc. You will amaze yourself and your friends at how much you can do by using the search function to get the knowledge you need to maintain and repair that 300se!

__________________
If it ain't broke take it apart and find out why.

1983 300SD, 4 speed
1994 C280
1987 300TD wagon
1996 HD Road King

Ride in Peace Eric Peterson, Harley of Macon