It's not that difficult at all. I'm using Acer laptop myself. To replace RAM on my laptop I just have to remove the center back panel with only 2 screws. After that just install new RAM to the available slot. Close the back panel and put those screws back. Turn on your computer and right click on My Computer and select Properties. Make sure that your new memory show on this screen. That's it. You are done.
Kingston Value RAM is the best in the Market cuz they offer life time warranty. But if you are not sure that you want to do it yourself, the place that you buy RAM from can easily install it for you. It take less than 5 min. to do.

As for new laptop, it's just all depend on your usage.
Sony Vio is good, but too expensive just becaus of SONY logo.
Dell has good after sale service, but it's too bulky
Toshiba is good also
To me I like Acer TravelMate 6292-302 G20
It come with Intel Centrino Duo Processor 2.0 GHS
(Intel Core 2 Duo Processor T7300)
Windows Vista Business
2048 MB RAM
200 GB Hard Disk (5400 rpm)
12.1" screen (Nice size to carry around)
Light weight (1.99 Kg) and much more.

Again, if you only use your laptop to check email I think that memory upgrade should be enough.