Buying Gears?

[98CobraConv]

I was planning on having them installed professionally. I know nothing about installing gears. I was just asking about FMS gears. I remember someone saying that they come with everything you need (pinion seals, pinion bearings, outer bearings, carrier bearings, and 23 tooth speedo gear). As of right now I am not planning on racing my car. It is a daily driver and only used on the street. That is why I was thinking of the 3.73's. I figured that would be a hella improvement over the stock 3.27's. If I go with 4.10's and still drive comfortably on the highway and roadtrips than I might consider getting those. As of right now the only modifications on my car are a K&N, Bassini X-Pipe with Cats, and a Borla Catback exhaust. I am going to get the gears then I will get a Steeda Tri-ax or the Pro5.0 shifter. After that I will look into suspension. Can I do the install on the shifter myself or will have to pay to do that? Thanks.