Step 1: Safety First!
Besides the complexity of maintenance and repairs for your vehicle there is also a certain amount of physical capability required. Particularly in this case you will be required to crawl under the vehicle and possibly lay in an awkward position while working. There is also an extensive amount of twisting and pulling required to remove the filter and oil cap. If these motions are out of the normal of your normal range, or if you have a back or shoulder issue seek the help of a competent professional. Once again it is better to hire someone to make the repair for you than it is to injure yourself in the process.
Last of all, do not attempt any repairs on a vehicle if your vision, decision making or physical abilities are impaired. This is the most dangerous thing you can do. You should never work on a vehicle while consuming alcohol or even hours after consumption. Fatigue, illness or even medications could also impair your judgement and ability to work safely. Safety is paramount, and if any of these elements are present when maintenance is necessary you should seek out the services of a trained professional. Do not attempt any maintenance under these conditions!!