Phildog75,
done this a couple of times now, wammers is right - get the heads off and its fairly straight forward, you'll need a good spring compressor. As you take the valves out ensure you keep the valves, springs, retainers and collets in order so you don't mix them up on rebuild. The old valve stem seals can be got off by twisting - I used a small set of mole grips, they're on there pretty tight, so mind you don't damage the valve guide getting them off. Do any cleaning and head work necessary. to fit the new ones this is how I did it. I found it was best to use one of the long plenum bolts ( clean it first so you don't introduce rubbish into your guide, then oil it with engine oil) with a washer and 13 or 12mm 3/8 (or 1/4) drive socket and a flanged nut. Set the bolt and washer up to go from the inside of the inlet tract through the guide, put the stem seal on the bolt carefully so you don't damage the lip, put the socket on so it cups over the outside edge of the seal and with the flat drive end of the socket put your flanged nut on
(you're making a vice effectively). Gently hold the bolt end with a socket and wrench, do the nut (opposite end) up with a spanner. Seals bottom out on the guides shoulder - you'll see this happen. Do yourself a favour and get LR guides, slightly more expensive but the go on and last. Good luck.