thesheep

I'm not actually a tree surgeon, just someone who has to cut logs occasionally but hopefully it's OK to post this question. I have a small Makita electric chainsaw that I've had for a few years, pretty light use. I went to sharpen the chain yesterday and found that I couldn't turn the chain by hand. Taking the bar off, I found that the drive sprocket is very stiff: I can just about turn it using a pair of pliers but not by hand. The electric motor still turns the chain OK. Although I have to say it doesn't seem to be cutting as well as it used to, even with a sharp chain. Should I have a go at taking it apart and seeing if there is something I can lubricate inside and how easy is that for a reasonably competent DIYer? Is there anything else to try? Thanks.