A regular schedule (once a week if used daily) of blowing out the vents will go far to keep the inside dust free (or near to). The problem really arises when the vents are neglected for a period giving dust bunnies time to develop. Once the dust has turned to dust bunnies, that's when disassembly would be needed since compressed air would simply blow the dust bunnies back and forth within the laptop.
As a personal note, don't be afraid to get into the laptop. There are quite a few videos and websites available for virtually all laptop models on disassembly, watch a few about your specific model. Some laptops are very simple to disassemble and others are very involved - you might just have one of the simple ones.
Hope it helps