1, yes although technically you're not increasing the Wii's memory as much as you are disregarding it entirely and loading off of a hard drive with greater storage.
2. Yes, you can autoboot using bootmii as boot2 and your sd card with the appropriate bootmii folder inserted when turning on the console. Or another way is to use priiloader to autoboot bootmii, then again make sure your sd card is inserted and holds the correct bootmii/uneek files.