First let's try identifying the grass using one of the links I'm attaching.  Since I don't know if you want to identify a grassy weed or a turf grass I'm including links to both:

MSU Turf Weeds.net

Weed Identification-Purdue

Turfgrass Weed ID-PSU

Turfgrass species ID & Cultivar Selection (E2912)-MSU

Turfgrass Identification - Penn State

turfgrass identification - Ohio State

Next, if the links don't help you ID the grass, you need to attach some photos to a return email.  Take a general photo of the grass in situ.  Then get a closeup of the grass plant.  Consider removing a grass plant from the soil and photographing it on a white backdrop as well.  If possible, get detailed photos of grass plant feature to aid in ID.

1.  Lawns in MI are almost always seeded with a mix of cool-season grasses (Kentucky bluegrass, Perennial Rye, Turf-type Tall Fescue, and Fescues).  Any (sun or shade) quality seed mix you find at a nursery, hardware or big-box should blend in when doing repairs.  Unfortunately the photos don't provide enough detail for me to ID any specific cultivars.  These links should help ID the grasses if that's needed:  

Cool Season Turfgrass Identification - PSU

Turfgrass identification - Ohio State

Cool-Season Turfgrass Basics-PSU

Establishing A New Lawn Using Seed-MSU

2.  The (grass) weed photos you sent are tall fescue (Festuca arundinacea).  It is a clump growing grass and can be controlled by digging it out and reseeding or with chemicals.  Go to this link, under grasses, to learn more.  MSU Turf Weeds.net

3.  MSU offers a soil test kit ($25.00) that is prepaid.  Order the kit, send in a sample (following the instructions provided) and they will email you a code and a link to view your results online.  More info here: 
 Don't Guess-Soil Test-MSU and MSU Home Soil Test-self mailer