First of all welcome to the forum!
I made a set of stands like the ones shown on this site for the rear of the bike.
http://www.gz250bike.com/forum/viewtopic.php?f=10&t=62 You can also use metal jack stands if you have them. They are placed under the swing arm close to the rear axle. With the rear up on the stands, you can use your scissor jack under the frame at the front of the engine to lift the front wheel just off the ground.
Remove the brake caliper and hang it from a bungee or piece of wire or string etc. Then remove the front axle, wheel, and fender. Loosen the fork clamps on the steering head (do not pry these to get more looseness!) and slide the fork legs out. Remove the caps being careful to hold pressure on cap while unscrewing. Otherwise the cap will fly off and possibly cause injury. Remove spring(s) and drain the oil out. It will be disgusting but that is normal for used fork oil.
Follow manual instructions for replacing seals. Sometimes (after removing circlip of course) the old seals can be tough to get out. Use the "slide hammer" technique of sliding the fork lower forcibly down the fork tube to "hammer" the old seal out. A properly sized piece of pvc plastic plumbing pipe works well for driving the new seal in. Measure the new fork oil carefully you want exactly the same amount in each tube.
I would recommend using at least a medium 15w fork oil, and 20w will firm up the ride even more. More money than ATF but worth it! The bike will handle and corner better. Good luck! This job is really pretty easy.