Cary SLI-80 owners. Questions

I recently bought this amp on A'gon but find the manual lacking. This is an older version with the chrome chassis and KT-88 output tubes. There are two switches on the top of the chassis that I assume are for switching between the 40w and 80w but don't know which is which. Unfortunately it's been in the shop as the shippers dropped it and broke some important stuff so I can't do an a/b comparison. Also can I switch output tubes or do I have to be careful about frying it? I'm new to tube amps and I can't seem to get info from Cary. Thanks.