Two possibilites - under $200
1) Send the old slides and negs for scanning. It is not that expensive.
2) Do as I did: attach a thin white paper sheet on a glass picture frame, and a digital camera on the opposite side of the frame than the slide projector. The slides need to be oriented in such a way that they come out the right way when taking the picture. Remote control for the projector is very helpful. Align everything well.
This way you can digitize slides at approx. 5 secs per slide. Your digital camera also improves the luminosity balance of each slide, but usually you need to retouch all. Dust is your worst enemy.
3) To scan old negatives I have used a cheap $ 60 neg scanner, but the result is only passable. Some of the scanners are nice because they convert the color negative to positive automatically (or - my Photoshop Elements does it - I'm not sure). These scanners often illuminate the neg unevenly - one side gets darker than the other.