I've solved , to my satisfaction , part of your problems
I have a 500GB external drive [ a WD Portable one ] on which is my Aperture Library and all Aperture work is done using that Ext Drive .
My MBP came with the original small amount of memory , but was very easily upgraded to the 8GB Max thanks to Crucial [ no I didn't do it - have hand problems , but a friend did it for me and even he commented how easy it was though you do have to be very careful with the minute screws as they are not all the same length !! ]
I'm not using a SSD .
Oh and I had a battery replacement under Apple care - the genius picked up there was a problem - I hadn't.
If a thing ain't broke --- DON'T FIX IT
Experienced in making a mess of things
2 x MacBook Pro on OSX 10.6.8 ,Belkin N Wireless Router , [ sssh - and a PC wired lappy using XP Pro ] all on Virginmedia