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OREGON at http://www.oregonchain.com has a great FAQ on maintaining, adjusting and sharpening your chain. This site also covers some safety issues, when to replace your chain or bar, and the different types of bars and chains on the market.
STIHL USA, at http://www.stihlusa.com, is a very popular manufacturer of chainsaws. They have full length safety manuals available at their site for download. These manuals include proper cutting techniques and also a maintenance chart to help you remember what needs to be done. Though the STIHL name is ubiquitous in the manuals, these manuals are very generic and can be helpful to anyone.
I am unaware of any links to sites dealing with actual chainsaw motor repair, but that is perhaps a good thing. You can purchase service manuals for chainsaws at a local dealer, but be aware that there are skills and tools needed that are peculiar to small motors, making this a somewhat expensive and time consuming sideline. Unless you want to take up small motor repair as a hobby, of course! In my experience chainsaw motors are very reliable. If you perform regular maintenance, keep the saw clean and don't drop the saw off too many trees, you should not have to do any major servicing for many years aside from chain and bar related issues... well within the abilities of most handy homeowners.
I can't broach the topic of chainsaws without at least mentioning safety, a chainsaw being one of the most dangerous tools you can own. And the most important safety issue in using a chainsaw is the condition of the operator... you! Using a chainsaw when you are not stable... mentally or physically... can lead to some of the most horrendous injuries imaginable. I have cut at least a hundred cords of wood over the last 25 years... no Guinness record but enough to have had a few close calls and a few minor (fortunately) injuries. When something bad happen with a chainsaw, it happens very quickly. The more stable your footing; the more your mind is focused on the work; the better condition of your saw and chain… the better your chance of survival... intact.