get a water pump kit like the one posted above, and just do it. theres some things you have to know to put the lower unit back together properly, seals go here and there, gear needs to be in forward, etc... but its nothing that isnt addressed in MANY youtube videos. its an hour job if you've done it before but expect to spend a couple since its your first time. as mentioned before since you're pulling the lower unit apart you'll need fresh gear oil. i suggest the quicksilver outdrive lube and you'll need almost 2 quarts and its about $12 a quart, you will need a special pump to put it back into your outdrive (available at west marine as well... under $20) since its pumped up from the buttom to the top to prevent air pockets. you should be replacing your gear oil every year. while you're at it, inspect your anodes since you'll be removing the rear one and have easy access to the front one.
