Even if you have some electronics experience I'd advise great caution, valves usually have high voltage DC supply lines which can be live even when the amp is switched off. What looks like charring can just be caused by a component frying, the fuse wouldn't allow excessive currents to flow. Electrolytic capacitors are among the commonest components to die, and valves can go faulty too because they operate hot so are under a fair amount of stress.
My advice would be: First buy replacements for all valves and electrolytic capacitors, several more fuses, and a low value resistor (say 4.7 Ohm).
Use the resistor (carefully, don't touch the wires with your fingers) to short out all the electrolytic capacitors, before removing and replacing them. These capacitors MUST be connected the right way round. Replace the valves one at a time. Have a really good look at the circuit board, often you can tell if a component has fried, because it is blackened or gone a pale colour because of overheating, or has a strong burny smell. If you suspect a component, find out what it is and replace it with an identical one.
If a capacitor has shorted out it may have also damaged the power supply rectifier, this may be a single unit or 4 separate diodes, and should be quite cheap to replace.
After all this, put a new fuse in, and switch on your amp - may the Force be with you !
Just so you know where i'm coming from, electronics engineers often find that replacing the usual suspects is quicker than doing a lot of testing and finding that it WAS the usual suspects all the time, so if they get a repair job like yours, they'll very likely replace all the bits I have mentioned anyway and say they have given your amp a "service".
Even if none of the valves was faulty it's routine to change them for new while you are doing the repair, unless the amp is brand-new and the valves are hardly used. Chances are that if your fuse doesn't blow again, and there is no funny smell, you have solved the problem.