The difference between having it done and doing it yourself can be huge. If you can find a frame you like (11x14 frame with mount board and 8x10 cutout) for around $25 to $30, go for it. Having it done by a professional framer, you can expect to pay ...
One way is to shop at thrift stores or flea markets, buy the frame/photo for cheap remove the photo and paint your frame. You don't have to buy a new frame. If your handy you can make your own.
I've ordered from this place before: You can create your own frame. You're not going to fit two 5x7 photos into an 8x10 frame, though. You'll want to go a little bigger! Get a frame about 8x16 or larger and have your mat cut for the two photos. Here ...