Importing MPEG-4 AVC/H.264 to Imovie

First off - my specs:

2008 Macbook 2.4Ghz Intel Core 2 Duo, 2GB 667MHz DDR2 SDRAM running Mac OS X Lion 10.7.5.

iMovie '11, vers 9.0.8

Just bought a canon t4i, with hopes of shooting/editing HD video (1080P) using imovie.

1st problem: Imovie does not recognize my new camera, so i'm not able to download movies. Format is MPEG-4 AVC/H.264. I'm not using a card reader, i'm using cable supplied with camera. Iphoto is grabbing the pictures just fine, and is even grabbing the videos too (not sure why). How do i get iMovie to recognize camera? Conversely, if Iphoto has done half the job, how do i move the videos from iphoto to imovie?

2nd problem: Let's say we solve the first problem, do you think my Mac can support the large files? In other words, will iMovie be sluggish due to the large filesizes? Question: Do you tink I should be dowloading as original, or "Large" (my use is mostly appleTV and some youtube).

3rd problem (bonus): I'm quickly running out of space on the mac. I have a 2TB Time capsule, which i only really use for auto backups. Lately I've been dumping archive video footage on there. I've read on this forum that I should consider dumping the video directly on the TC, perhaps even buy a secong ext hard drive strictly for my video files. Before making that purchase, I'd like to know your opinion on my Mac. It's really running sluggish lately as it nears full capacity.

Thanks in advance,

Matt