If you're on a PowerBook running 10.4.11 you won't be very happy at all, as it won't run 😉
Aperture is a fair bit different to Elements. It's more focused on editing/keywording many photos, versus the "one at a time" of Elements.
If you have a fairly recent machine (< 1 year old) it's certainly worth downloading Aperture (there's a 30-day free trial on Apple's site) and giving it a go. Only you can really know for sure.
Apps like Aperture and Lightroom are primarily images-management apps with limited editing capability; iPhoto is a free beginner version.
For significant editing but poor images-management one can use very expensive Adobe Photoshop, less expensive Adobe Photoshop Elements, Pixelmator or (free) GIMP.
IMO DSLR photogs should own/learn/use one app from each of the two categories above.
Specific to only removing distracting background elements are apps/plug-ins like KnockOut2.
You are using Elements, so editing is covered. For images management use iPhoto for free until it seems limiting. Only then embark on the one-time 30 day Aperture trial, realizing it it hardware-intensive (your MBP is adequate if RAM is maxxed).
