It's not too hard if you have a scanner that can do slides.
The resolution of the scan should be the key. Most decent scanners nowadays are capable of at least 600-1200dpi scanning...and 600 dpi should be plenty for slides even for large prints up to 8x10 or so. When I scanned the above slides at 600dpi on my scanner, they came out to approximately 3500 pixels on the longest side...so quite large. From there, I could edit them in my Paint Shop pro program for color, contrast, etc to account for some fading, scratches, etc on the old slides, then crop them to get rid of edges and borders...usually I use a cropping template like 4:3 or 3:2...and end up with a final result around 2850 pixels on the longest side. I save that for keeps, then make another copy which i downsize to 800 pixels, run some unsharp mask to sharpen them up a little, and those are the versions I upload.
The biggest problem I had previously was that my decent scanner only projected light from the bottom, so to scan slides, they either came out way too dark, or I had to lay paper over them and shine a flashlight down to 'backlight' the slide for the scanner. I decided since I was really going to work on this project with many old slides (not just Disney...I've got cruises, vacations, etc going back 20+ years), I would buy a scanner capable of slide scanning specifically - meaning the scanner had backlighting capability built in to the lid. I bought an $80 Canon flatbed scanner that can do 600dpi, has backlighting, and can handle 4 slides at once in a slide-holder. It made life easy, as the scanner first does a test scan, figures out where the photo parts of the slides are, and offers you the 4 frames in thumbnail view, already cropped free of the slide frame. You can checkmark the ones you want to scan, or edit the cropped border if the scanner got it wrong, and then let the scanner do the work. It takes roughly 4 minutes to scan all 4 slides, at 600dpi each. As soon as it's done, it deposits the 4 scans into the photo editing suite of your choice (I have them laoded into PSP8), so you can edit and save.
I'd recommend picking up an inexpensive slide scanner - you can find plenty under $100. But if you don't want to or can't, you can get by using any flatbed scanner by putting the slides on the glass, laying a diffuse white paper, cloth, waxpaper, etc over the slides, and putting a bright light source over them (the more diffuse and bright the light, the better the results, so you don't get 'hotspots' in the scans).
Set the dpi to 300, and you should end up with photo sizes similar to a 3mp photo...At 600dpi, you should be in the range of a 6-8mp photo. That'll give plenty of leeway to crop, downsize, and post at this size!
