Yes, the pushrod seal can be changed with out splitting the cases. Ordr two seals, in case you mess up the first one.
Pull out the rod. pull the seal, I use a large screwdriver. Care you don't scratch the case. The edge of the hole is sharp. You need to bevel this edge. Just enough to break the sharp edge.
A thin coat of Three Bond on theouter edge of the seal and carefully slip in the new one. I have a large Philips head screw driver that just fit in the seal. I put a large washer on the screw driver, then the seal. I put the shaft of the screw driver in where the push rod goes. The screw driver guides the seal straight in. The washer stops the seal from being pushed in to far.
You might want to replace the bushing in the end of the tranny shaft if you haven't yet. If the bushing is worn the push rod can move sideways and put more pressure on the seal and wear it sooner.
On Mike's XS site, in the tech section he tells how to replace the bushing.
On the leaks from the front guide bolts a thin coat of the Three Bond will seal them. There are two places for oil to leak there. The bolts with the ten mm heads and the larger chrome plated bolts the small bolts go thru.
Be carefull on the torque on the small bolts. The aluminum that the guide is made from will strip out if over torqued.