need help on engine/outdrive purchase

[gingko]

I have a 21'bayliner explorer with a dead 1983 volvo penta 125hp engine. I want to replace both engine and outdrive myself thinking of a 135hp volvo penta with new outdrive. Is this a good unit? Can I do it myself with an appropriate amount of blood sweat and tears? Any thoughts from all of you that know more than me? Can any of you recommend a good place to buy a unit? Price is a critical consideration. Thanks in advance to all of you and positive thoughts, bob