Several

Question
I have had 2 guinea pigs for about 2 or 3 months.  I have a couple of questions.  The first is regarding bedding.  We have been using Carefresh which is very expensive.  I'm wondering if it would be okay to use the pine in conjunction with the Carefresh to help cut costs a little.  The second is regarding housing.  We keep ours in a cage in the house most of the time.  But if I set up a pen in the grass, in the shade of course, would I have a horrible problem with fleas in the summer?  And, if so, is there someway to treat this.  By the way, these are long haired guinea pigs.  I'm also a bit afraid of cutting some of their nails because they're black and I can't see where the "quick" is.  I don't want to take them to a groomer, again because of cost reasons.  Do you have any advice on this and how often do they need to have their nails clipped?  I think that's it for now.  Thanks in advance for your advice.

Answer
<<The first is regarding bedding. We have been using Carefresh which is very expensive. I'm wondering if it would be okay to use the pine in conjunction with the Carefresh to help cut costs a little>>

Do not use regular pine, only use it if it is Kiln Dried. Some cheaper alternatives to Carefresh are Aspen, Kiln Dried Pine, Yesterdays News, Cell Sorb, Pelleted Pine and Fleece.

<<We keep ours in a cage in the house most of the time. But if I set up a pen in the grass, in the shade of course, would I have a horrible problem with fleas in the summer?>>

No, fleas are species specific and will not stay on a cavy.
However, you may have a problem with species specific lice, which can easily be treated with advantage.

<<Do you have any advice on this and how often do they need to have their nails clipped? I think that's it for now. Thanks in advance for your advice.>>

Cavies should have their nails clipped at least twice a month, especially Long haired cavies as their nailes seem to grow long, thicker and tend to curl more often then other breeds. Use cat clippers or human clippers and only take off a bit of nail at a time. If you cut the quick it will hurt, but it won't be life long effect and the bleeding can easily be stopped with a Baking soda or flour paste, or quick stops that can be purchases at pet stores.