People hate it when I do this, but I haven't angered anyone yet today so...
Will I have to make any mods to my 15 sport to mount a bipod on it?
Yes and no. There are a couple of bipods that mount by clamping on the barrel. This is usually a poor idea and will affect accuracy. Plus those are usually very flimsy devices. So, if you just have to have a bipod, and you want a decent one, a modification will have to be made.
What bipod is recommended?
I recommend no bipod. While there are some good ones out there, they are all less stable than a sand bag, tree, rock or backpack. They add unnecessary weight and if not used properly, will affect accuracy. One attached to a free float forearm is best. One attached to the barrel or drop in forearm will alter your zero. How much it alters it will vary depending on several factors.
Even so, if you just have to have one, look to Harris.
What strap is recommended?
I recommend no strap or sling. Unless you will be walking long distances, or have to carry it all day, the sling will only get in the way. They have a tendency to get caught on any protrusion whether in a house or out in the field. They get tangled with other guns as they are put in the safe. If not practiced with, they get caught on your body as you raise the gun to shoot.
However, if you just have to have one, I recommend the Magpul MS1. It's a little more expensive, but easily adapted to whatever conditions you'll be in. The MS3 is also good, but the MS1 is easier to adjust with one hand. Yes, I own both.
Resist the urge to get a single point sling. Unless you're clearing houses, they are not as comfortable as a two point sling. The two point sling spreads the weight out over your back more. The single point tends to put a lot of pressure on your neck. Yes, I have two of those and have used them in multi-day classes. Get a two point.
Again, it's better to have no sling.
The problem is I can either look at the target or look at the sights.
This is not a problem; look at the sights. Your focus should be a hard focus on the front sight. The target will be a little blurry.
If using magnified optics, the focus should be on the reticle. If it's a good optic, both the target and reticle will be in focus. If it's a lower quality and you have to choose between sharp focus on the reticle and the target, choose the reticle to be focused on.
What optic would you recommend? I will be target shooting out to 300 or so yards and will eventually hunt with this.
thanks
Ooooh, now I can really get spun up.

I won't though.

I will say this, don't try to save money on the optic. If there's one place a little extra money will help you, it's the optic; even more than the rifle itself.
Now, before we can guide you properly, we need some more info. How will you use the gun the
most? I know you said targets to 300 yards and hunting (eventually), but what distance and type of target will you shoot at the most? If you're looking for bench rest, smallest group possible, style of shooting, you'll need magnification. If speed of acquisition and short yardage (less than 100 yards) is the main use, then a red dot or HWS is better. So, think about it and tell us what the main use is and we'll help guide you in the right direction.