Replacing or installing a garage door can be a tricky process. There are many different factors that need to be addressed if you wish to plan and organize everything correctly. One of the most important factors that should be considered would be your budget. You need to be able to compare garage door prices in order to find a financially viable option for you. In order to determine this you would need to have first determined exactly what amount of money you can afford to spend on the installation of a new garage door.  
It is important to note that the cheapest option may not be the best when it comes to garage doors. These doors need to be strong enough to protect your possessions. Many people park their cars in their garages and store all their tools here as well. These items are all quite valuable and a garage door needs to be able to secure this area. If you simply opt for the cheapest option then you may end up with a garage door that is inferior in quality. If you spend a bit more money and buy a high quality product then this decision can actually end up saving you a lot of time and money in the future.
Another factor that can be considered is whether you would be installing the garage door yourself or if you plan to hire someone to do it for. Professionals can charge quite a bit of money for labour. If you do not have a very large budget for this and if you are a naturally handy person then you should consider installing the door yourself. You can request the help of a few friends as well and this can end up saving you quite a lot of money. However, it is important to note that this should only be done if you are very confident in your abilities. Garage doors need to be properly installed and if you are not sure that you can execute this task perfectly then you should hire a professional instead.