Airport extreme and Airport express problems

Hello – I am new to the forum and have a problem with my Airport express base station and airport extreme. I have spent several days doing a hard reset on both the base station and the airport extreme and then trying to re configure them. At one point I had it working and then tried to install a second airport base station and crashed it.
Can I Have more than one base station -- I have a stereo in the living room and another in the kitchen/dinning room and would like to hook up two.
I am using airport utility version 5.2 and the airport setup assistant 3.4.3. If I try to update the software I am told they are both current.
I got to a point today where i saw both the airport extreme and the base station in the utility and it told me I had to switch networks to configure the bas station and then after I answered yes it went looking for the base station and never came back
I need detailed instructions and would appreciate any help.
Thanks