Trans/Drive belt replacement on a Scag SMWC-61

I need to replace the drive belt on a Scag SMWC-61 ( Kohler Engine 27HP) . I'm pretty sure that I have to remove the cutter/deck belt 1st, since the drive belt looks like it belongs above it. ( I have lots of experience on the deck belt install. I have a habit of sliding off when I 1st engage the PTO. I've tried low-med-high rpms. Still happens. Any advise on this problem? ) Back to my main problem. Is there any extra advise I can get on the Drive belt replacement? Or, is it pretty much straight forward? I have manual for belt routing. { Extra stupid question. This belt has notches or "teeth". Is this for extra "traction" around pulley's?}