How do i check the size of my spokes? i need to replace a few of them? I need to figure out what size nipples too? Also what is a good brand of spokes? or where should i buy spokes?

Univega viva touring with 27" rims..

I ride 10 miles a day.

You need a mm graded ruler where the grading starts right at the end. Hook the elbow of the spoke over the end, see how far it reaches. To determine gauge/thickness/nipple size a vernier caliper makes the job real easy.
If you're buying from a shop (often the best source for single/few spokes) just bring them a sample spoke and they'll sort it out for you. Remember that disc braked and/or externally geared wheels often take different sizes/lengths left/right.
I use mainly DT, but wheelsmith also has a good rep. Nothing wrong with Sapim, but they tend to be expensive.

If you need full sets you can buy over the net. For the occasional spoke a visit to a shop is often cheaper.

You are probably better off going to a LBS and having them replace the spokes and true the wheel. That said I usually buy spokes over ebay. If a spoke broke then the surrounding spokes may have been weakened, so replace more than just the one that broke. Buy nipples from the person you buy spokes from. You can probably can true the wheel on you bike just eye balling it. As to length search on [measuring bicycle spoke length]. Diameter is probably 2mm but should be confirmed. It is possible that the rim was damaged at which time you will need to rebuild the wheel or buy a new one.