These types of issues are not often described in a manual, you have to figure it out on your own, that's a big part of working on cars. If access is a problem, you may need to remove whatever is in the way, or you need a tool that can get to the bolt in question. Without seeing it, I can't offer anything else, sorry. Good Luck
I just changed one of these on my 2.5L. The engine is relatively easy to repair. But the water pump can be a nightmare. The alternator and bracket have to be removed. The main upper engine mount bolt has to be removed to allow for the alternator/ac compressor bracket to be removed from the engine in order to remove the water pump.
The water pump is mounted by four upper bolts on the engine block. The real catcher is the extremely LONG bolt that slides through the pump to the engine block. You must loosen that bolt and remove it as you remove the water pump assembly. AND REMEMBER. That bolt must be inserted into the pump as the pump is reinstalled. Otherwise the bolt will never go into the whole because the radiator will be in the way. Believe me I learned the hard way.
The thing is that only the front part of the water pump has to be replaced. So all hoses and such can remain installed. But, there's no way to get the 10mm bolts out without removing the timing belt sprocket. So you can either remove that, or do the steps I mentioned above. I prefer NOT to mess with the timing. It just takes longer for me.
But its your choice.
Either remove the timing sprocket in front of the pump. Then remove the 10mm bolts to replace the water pump. Or remove the ac compressor bracket and remove the whole water pump assembly. Put the new pump on it. Then reinstall the whole thing in reverse, while remembering to insert that long bolt into it as you mount it to the engine.