brokesomeribs,
Sounds like you need to get clear on what route your team is planning to climb.
Neither the highly popular Normal Route or the Polish Traverse (Vacas Valley approach) present any glacier problems.
The Polish Direct is a different story and frankly, based on your experience, that may be a problem for you.
Route considerations aside, in terms of training for Aconcagua the biggest challenge faced by most climbers is a combination of the altitude and the length of the climb. Climbing Rainier or any other peak in the lower 48 at most is an effort of just a few days. Climbing Aconcagua is a three week effort for all but the strongest and most acclimatized people. Good preparation for Aconcagua includes as much multi day hiking/climbing as you can manage to fit in before your trip. Similarly, the best way to prep for the altitude is to be as fit as possible at the start and to allow yourself plenty of time to get up the mountain.
Good Luck and Have fun!
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