The first three changes are just a matter of unbolting components and swapping them out. The literature that comes with the shifters and der is enough to cover the methods.
www.parktool.com under the repair button has an extensive writeup on basics of bike repair and can prompt you over the sticky parts.
You might as well do 9spd as the cost differential is minimal and you get an extra gear in the 15-20mph range that is nice to have. Try places like
www.hostelshoppe.com,
www.poweroncycling.com and
www.gaerlan.com for forks. Don't have any suggestion as to sources otherwise. You are going to drop
some bucks on this for reasons not entirely clear.