My 1976 25hp Johnson has a blown lower unit but I have access to another engine similar year with a blown top end. Other than a manual, are there any special tools (ie. gear pullers or alignment tools) that i would need to perform this job? I also would like to replace the impeller and examine the new lower unit to make sure its ok. Am I biting off too much? I do have moderate mechanical skills on cars. Thanks for your opinion and website being available to ask such questions.<br /> Michael