clean/replace friction tuning pegs?

I have a Slingerland May-bell banjo ukulele which I love, but it is absurdly hard to tune. The pegs are inconsistently resistant to turning, and the plastic part can sometimes move without affecting the pitch. I'm thinking that they're just dirty inside and could use a good cleaning, as the thing is about four times my age.

I don't know much about tuners, but these have a 1:1 ratio, making them friction tuners, right?

Can I just take them apart, clean 'em and spray them with WD40, or will that prevent them from holding pitch? Or would it be better to just replace them?

Refitting them them is not that difficult. I'd encourage you to fill out your profile, maybe there is a member or some other good resource in your area that will help.