MB543LL/A - Few questions for a new mac user :)

1) Standard SSD's use standard SATA connectors. the MBA uses a special blade type SSD that uses a custom SATA connection and also takes up significantly less room. Most standard SSD's are based around the 2.5" laptop hard drive standard while the Blade ssd is nothing more than a small printed circuit board with chips on it.

3) You cannot "for free" upgrade to lion. it is a $29.99 purchase that you need to do through itunes app store. it downloads and installs online.

2) being an older Air (not the current 2011), you can make a Lion install CD based off the download. there are HOWTO's avilable on the site, just not sure where that will guide you through it. However, keep in mind the Version of Lion downloaded and installed on current 2011's do not play well with eachother.

 

1. Yes you can. There are SSDs compatible with the 1st and 2nd gen Airs, one of which can be found in this thread

http://forums.macrumors.com/showthread.php?t=1311207

Also see what suggestions the OP has got, coz he too is looking to replace his hard drive.

2. Since you have just 2gb of RAM (non upgradable) and new to Mac OS, I would suggest you stick with OSX Snow Leopard. The learning curve is much steeper with Lion IMO and also your machine will handle SL better.

Congratulations on your purchase and feel free to ask any more questions that you might have. Welcome to the Mac world