When my friend borowed my 1040STFM from me and managed to spill nearly a bottle of Coke over it, when he gave it back the keybourd needed to be cleaned cearfully (lots of little rubber things that just run away when you turn around).
The motherbourd was also in a sticky state along with the case, my friends did not think this would be a good idea but I simply removed the power supply, floppy drive along with all the shielding and simply took it out side and hosed it down. The machine still works fine though.
You may have found the they left the thing on with liquid in side which killed a few other bit on it.
If you do not have a mouse then you can use the arrow keys by holding down control or Alt (I forget).
This site also has diagrams; along with menu (game) disks and some utils;
www.atari.co.uk
This site has a large number of utils on it;
http://www.geocities.com/Tokyo/Temple/9537/PRG-IND3.HTM
