Installing exhaust

Not being a dick but if you have to ask, maybe you should have someone else do it, even though its one of the easiest mods to do you could still have problem if you are not handy with auto tools !

But if you do try it dont tighten anything until you have everything in its right spot and the fitment the way you want it !

Couple of points for ya...
You will put more time and care into it than any shop ever would. I'd almost guarantee (if you are an anal Mustang Owner like alot of us are) you'll find some part of it that the shop didn't do the way you'd have done it yourself. It'll hang too low, or the tips won't be even, will be sticking out too far, etc. Been there, won't do that again.
If you need a new TOB, I'd put a new clutch it it.
If you need a new TOB or a new clutch, they'll likely be dropping the midpipe anyway. Having transmission work done is the perfect time to have exhaust mods installed.
This is a great DIY mod...it's just taxing on your back, but otherwise, the work effort itself is really simple and straight forward. Air tools help (nearly required on a midpipe) but are not necessary on a catback.
The LM2 is a GREAT catback - super high quality and I just loved the tone. My wife had it with an off road X on her 01 GT. The double wall tips are really nice. I've gone through a lot of different catbacks and the LM2 is the one I would buy again. Excellent choice my friend.
Do you have a midpipe other than stock? Once again, this is the time to buy and install one.

So there is my nickel's worth. Best of Luck.

If you have the tools and space I say go for it. The best way to know about your stang is to do the work yourself. If this is your first time just be patient and you'll be fine. Like the others have said if you’re getting the tob replaced this is the perfect time to go with a high flow or o/r midpipe. If you come across questions during the install run a search through the forum or ask there is a wealth of knowledge on here.

Life is too short to do exhaust work, take it to a shop.

If you are installing a cat back, its a matter of disconnecting the existing pipes.
(4 bolts, 2 on each pipe) then bolt back the new pipes. The Exhaust tips screw on with a hex key most likely so you can get them to line up perfectly on the back of the car. just back your car up on tall ramps, so you can finagle the existing pipes out without having the saw them out.

Its stupidly easy.

the midpipe is a little bit more involved only because you have to jack up both sides of the car to get under it. but the concept is the same. unscrew the bolts on each end of the pipe, unscrew the O2 sensors, put in new pipe, screw in the O2 sensors.