[MilCom] frequency listening question

[odyslim at comcast.net]

Hello,  Please excuse this question. I have very little experience listening
to the UHF/ VHF frequencies. My retirement is due June 30 and I will have time
to begin listening to UHF and VHF. I have been putting together a station
so I can monitor several frequencies at one time. What I have is 4 ICom IC-R100's
and a PRO-2006. Before mounting all of the radios in the rack trays,  I want
to change all of the batteries. Each R-100 has 2. 

 Question 1: The manual says to have it done at an ICOM dealership. Why?
Will damage the radio somehow?

 Each R-100 has 3 antenna outputs. 500kc-50 megs, 50mhz-905megs
and 905 megs to 1800 megs. Question 2: Is there anything to listen to above
905 megs? My reason for asking is I want to avoid making up the extra 4 patch
cables ( 4 radios) and also want to avoid the extra multi-coupler if I can
So what is up above 905 megs?

 I know this sounds rudimentary to all of you experienced listeners but I have
 been monitoring HF since childhood. UHF/ VHF is a new game for me. the only
frequency I know is the Tipton Airport freq (MD). I live very close and enjoy
listening to that.

 My HF section is 4 Yaesu FRG-100's They will also be rack mounted.

 I have an old C&P telephone company rack that has nice doors front and back. 
There  will be plenty of room for the radios, A 35 A/H gel cell battery, charger 
rig-runner, power supply,  multi-couplers ect. This will be my 12 volt set-up.
I have a bunch of R-390A's I use on a daily basis as well.

 Any how, if anybody can help with the battery and frequency questions, I would
greatly appreciate the help.

 Oh, My antenna is a discone mounted up on the roof of my house. Will that
be sufficient?

Regards, Scott