look here in link #5 I have the seals info listed off of the seal.
You shouldn't need to split the cases to replace the seals they will pry out drill a small hole in the seal and hook it to pry it out be very careful not to nick the crank or the housing. Take your time on this. To install the seal lube the seals lip with grease and use a seal driver if you don't have the driver a deep socket the same size as the o.d. of the seal will work drive it flush with the case or just a little more than flush with the case. Make sure you don't ding the crankshaft if you use a socket.
If you take the numbers to (Advance Auto this is a parts store you might have something else where you live ) they should be able to cross ref. the sizes to get you the seal/seals, see if you can't get a double lip seal better than a single lip seal for these engines.
The screws are not soft you need to use the correct fitting screw driver on the screws head.