Personally, if I were servicing my forks once every 3 years, I’d fork (lol) out the money to have them done properly, to an incredibly high standard, with the exact right oils, seals, grease, torque and spares.
IF you do it yourself, you’ll probably spend about £50 – 60 buying all the stuff you need (in bulk, as you’ll tell yourself it’s cheaper, and you’ll do it more often, but be honest… you know you wont).
OR…. you can spend £80, which spread over 3 years less than £30 a year!
Don’t be a cheapskate, go and get it done proper.
For info, I’ve been servicing my forks for years, I do a lowers service regularly, but the most important thing is that I have enough tools, kit and spares for if something goes wrong, I don’t need to send it off for repairs, after forking out (lol) money to start it off and bodge it myself.
Ricks