advise from a pro...

areotov, even though I am not a pro, I think there are a few things I can contribute. Logic board repair will require a few things.

To start with you need to know and understand schematics. Try to get as many schematics for the devices you are going to fix. You will not get schematics for all devices, maintain a good supply of logic boards that you can use to identify components.

Next invest in a few good tools. A good soldering station as well as a soldering rework station are imperative. Sounds impressive but it really is not that bad. I use a $150 station and it has served me well. also, you will need good meters. Get a good multimeter and a capacitance meter as well as a good thermometer. I use a K-Type digital thermometer with different thermocouple probes. This is needed for reflows. cost for those is around $30 Also invest in a good IR thermometer, this will allow you to measure IC's on logic boards that are having issues. Remember that broken IC's can get hotter than the others or remain stone cold. You can get those for around $30.

You will need plenty of good task light, and a magnifying source is a must. I use a tabletop mounted flourescent light with 5X magnifying lens. Take a good look at some of the components you will deal with. Package size for SMC goes from 01005 (0402 metric): 0.4 mm × 0.2 mm (0.0157 in × 0.0079 in) to 2512 (6332 metric): 6.4 mm × 3.2 mm (0.25 in × 0.13 in). Soldering those without magnification is almost impossible.

I have two more items that I use quite often. One are smart tweezers and the other is a USB microscope. The microscope definitely helps soldering the smaller components as well as visual inspection of logic boards. The smart tweezers help to identify components on a board for which I do not have the schematics. Neither one of those items is very expensive, but definitely very useful.

One thing you can not buy, is skills. Those you have to develop. Read, read a lot about the components, learn to understand datasheets and practice, practice, practice. Know and accept your limits so that you will not get in over your head. Just my two cents, best of luck to you.