Two questions. Adding oak chips in a secondary. 4 gallon batch in 5 gallon secondary

I really would love to add some oak to my "power porter".
Here are two questions:
1. Porter has been sitting in the primary close to 3 weeks. I've tasted it and I think little bit of oak would really do justice to my first brew (porter and hefe are pretty much two kinds of beer I usually drink). I am thinking I might want to do 1-2 weeks in a secondary with some hungarian oak chips. What do you think about the ideas?
2. My secondary (glass carboy) is a 5 gallon one. My batch is 4 gallons. How do I minimize the risk of infection etc. and oxidation, if adding bit of oak for couple of weeks before bottling would do it good?

I have no idea and am by no means even a novice at brewing beer but I have nothing else to do at the moment so I will give you my opinion. I would guess that you might want to boil them but that might leech out all of the flavor/aroma. you might think about baking them in the oven for a period of time. or even the microwave I think if long enough this will kill off all stuff but Im not sure. The wood shouldn't really get hot in the microwave because microwave radiation heats up water not wood.

Again wait for a real resonse from somewone who knows what they are talking about but those are my thoughts.

I use oak in an ale. The chips comes pre packaged. I have boiled the chips in water on the stove and added it all to the fermentor. The last few batches though I just add them to the fermentor. I noticed that the boiled chips had a less of an oak taste I wasn't looking for. I have not gotten an infection by just dumping them.

I must be lucky or it is harder to get an infection.

I added 4oz of medium toast Hungarian oak chips. I have also use French oak when I can get them.

I agree that if it's a strong beer you shouldn't have any problem just throwing the chips in there. If you really want a little punch soak the oak chips in good bourbon for a few days then put the oak and bourbon in the secondary. As far as your second question, don't worry about the extra headspace in the carboy. The last bit of fermentation that happened in secondary created enough co2 to put a "blanket" of co2 over the surface of the beer keeping o2 out.

If you are really concerned about the headspace in the secondary, boil a little water with an ounce of sugar and add that. It will create CO2 to fill the space. It's simple sugar, so the yeast will eat it without multiplying.