No need to take it to a shop, removing and replacing the window is pretty much straight forward. Get butyl tape, I used eternabond, but that is very hard to work with and to cleanup afterwards, I will not do it again. After removing the window, scrape off the old butyl tape and put new tape around the window opening. Replace the window and replace all the screws. Carefully remove all the excess butyl take and apply a bead of sealer around the outside.
Here is a You Tube video that will help guide you in the project.