I just did mine, it took all of 15 minuts to get the old transducer out, clean the hole out, and put the new one in. It did take me another 30 minutes to run the able up to the helm. (27' Regal) I am by no means an expert at anything.
It can also depend on the boat, how hard is it to get to the transducer, mine was in the open area with no access problems, how complicated is it to run the wire? How big is the boat etc.
If it is straight forward you may want to do it yourself, if it looks like it is going to be a pain in the a$$ it is well worth the two hour qoute!