Tractors are not my hobby yet but keeping a great lawn has been for the past several years. There are a few things you have to understand here. With Nutsedge there are tubers and nutlings under ground that you don't see and at this time of the year the sedge is a bear to get rid of. If you spray now you will knock down the existing sedge but it will come back next year and the year after and so on. It may take several years to get a handle on the sedge. Proper timing early early in the summer is the best time to get rid of the sedge because the tubers are small and easier to kill. You could try your local Lesco/John Deere dealer for Sedgehammer or some other product designed for the sedges. You need to check if there is a granular form or just liquid from Ortho.
As far as crabgrass again timing is everything. Applying a good granular pre-emergent when the Forsythia first bloom in the spring is the time to apply the preem. Products called Dimension come in either liquid or granular forms and can be spread over a wide area quickly. Dimension is only one pre-emergent. If you want to take care of it now the Ortho Weed be Gon Max with crabgrass killer works well along with other brands as long a you don't apply when temps are above 90 degrees. Really any product with Quincloric will kill the crabgrass and not the good grass. But make sure you check this out for your particular type of grass.