There are many video tutorials that can teach you how to do almost anything. That is why do it yourself projects have become incredibly popular nowadays. If you have a hydraulic power system with a damaged seal in the cylinder, you should not take a DIY approach because you might cause more damage to the system. Ideally, you should let a professional do the job. Start by searching the internet for reputable mechanical engineering firms with a great reputation in the industry. Ideally, you should give priority consideration to firms that have been in the industry for long.
Hydraulic cylinder seal replacement should be done on a regular basis. You should not wait for your system to start developing problems before you replace the system. The replacement should be done by a professional with years of experience in the industry as well as a fully equipped workshop.