It sounds like the bike speaks to you- a good sign. Aluminum is fabulous for dirt, but then different alloys really are different and different frame designs will make a big difference. I've ridden aluminum on dirt for years, and it's the stuff, very stiff for body englishing around and won't rust to peices from the ineveitable swimming trips . The fork really does eat the vibration, but remember that dirt doesn't even make the same trouble as pavement anyway. I started on a rigid fork, good for technique. Never got beaten up. I shudder at the idea of alu road bikes, seem very painful! But the stiffness of alu for mud sliding is great! You don't want a noodley frame on dirt.
Forks are set up for your riding style and weight; Manitou is totally superior equipment and broadly adjustable. I'm not familiar with the Scarab off hand, but the shop will adjust and change minor parts for your weight. Then you ride and decide how you like it and tweak from there. Everybody will fiddle with their fork, and high end Manitou will adjust in the feild for different terrain. You'll pick this up in no time once you put some miles in. Just make sure you get a good headset, like a Chris King. Worth every penny.
And repairs to frames? Once you break a production frame, it's history. Even if you weld a steel frame you screw with the heat treating and temper of one section and it will never be the same. By the time you strip it, weld it, reheat treat it, paint it- just buy a new frame. You may be in warranty anyway, and why take the risk of a faulty frame? The money will be better spent on your safety. You can repair alu but it's the same headaches, and you'll need a kiln for some alloys. Besides, if it's defect you'll be warrantied. Yeah, I went to welding school... A custom frame with tubes brazed into lugs is very repairable, you just replace the failed part. But those aren't the greatest on the dirt.
My 23 cents worth; Happy New Years girls!

Lizzy