I have the nikon D3000 also the D5000.The D3000 is a nice camera.easy to use takes nice pics.Came with 18-55mm lens 10.2mp.Only real downside for me is no live view
cost me 450 at meijer's.The D5000 is a nicer camera with more options.It is 12.3mp HD video has live view also takes nice pics.came with 18-55mm and 55-200 mm lens.cost at the time about a year ago 750 at Best buy.
neither camera has a built in auto focus motor built into camera body.Some of the cheaper lenses also have no motor so no auto focus.Unless you buy lens that cost more.
A few tips.If you go with nikon go with the V.R lenses (vibration reduction)cost a little more but imo worth it.
No matter what brand you go with if you ever buy used lenses make sure they work for what you really want.Even used lenses can cost some good money.Also imo never buy used unless you have to.
You always have to ask when buying camera If it is gray Market camera.DO NOT BUY IT IF IT IS.What this is is a camera that was made for say china that some how made it to a shelf here.Some of the components for a camera may not work here.some gray market may just be out and out fakes.The reason I say this is because it may Void the warranty and yes even the extended one you paid an extra 50 bucks for.
You said you want something you can use filters on.When it comes to filters it is never more true you get what you pay for.also there are different size filters for the different MM lenses.How ever many lenses you buy buy the same ammount of cheap filters When not using a lens keep a cheap filter on it it just helps to protect the lens glass.Even a small scratch on a lens will ruin the lens and a 10 dollar filter is alot better then a 200-300 dollar lens.
I think the most important thing is when in the store looking at cameras go with the one that feels the most comfortable in your hands.Trust me you dont want a camera that feels bulky in your hands.Good luck and have fun photography can be a very fun hobby and its a great excuse to get outside.