If the rear Crankshaft Seal housing has to be pulled off of the engine block, then there is a requirement to align the same in the right position on the end of the crankshaft because the seal is very sensitive and leakages from it are likely to occur if the housing has not been well aligned. First, the transmission is the item to pull out, then the driveplate. Open the rear cover of the automobile, and with a lot of precision, use a screwdriver to remove the Crankshaft Seal without damaging the crankshaft or the seal bore. The depth of the old seal before pulling out for new seal installation must be checked to ensure it is the same depth as the new seal is to be installed to check the bore of the seal in the block using a shop towel to remove all the dirt and oil. Lubrication of the seal and touching the sealing lip should not be done and the orientation of the seal must face with the correct part number. In an ideal world, one should use a seal installation tool to set the new seal back into place; if none is available, one should carefully use a large drift to set the new seal squarely into the seal bore and up against the rear cover. Last, put the driveplate back in and the transmission as well; if it does not want to go back on, then either get some new bolts or grind off the edges of the ones you have.