I did my stem seals when I had the head off.
Normal OHV spring compressors don't work. The PVC pipe thing on SOGI didn't work at all for me, not enough tension. I used a spring compressor that looks like a giant C-clamp. I used a piece of copper pipe, and cut out a rectangle in the middle of it, too compress the springs, and pull/replace keepers. I've also seen DSM guys use a wide deep socket with a square cut into the side at the end of the socket.
I forget the deep socket you use too push in new seal, its like a 8mm or something, you feel a first click, then push harder and you'll feel the second click, then its in! If its a older 7MGTE probably worth pulling the head too do a valve grind anyways (MHG if you haven't already)
BTW when putting keeprs back in, use a dab of white grease too keep them stuck too the stem, remember that you only need too compress the spring a bit too fit keepers in. My first time doing this took me a very long time, you live you learn I guess!