Sounds like he's given you solid advice! The siphon he's talking about is most likely one of the little hand siphon pumps you can get at walmart and most auto parts stores for ~ $10, not mouth siphoning like when teenagers used to steal gas (not that any of us has ever done that, but we've heard stories):thumbsup:.
As far as 80W-90 gear oil, it's probably the most common gear oil out there and available anywhere that sells gear oil. If that's the weight the manual states, you can't go wrong with it. I personally use a good synthetic like royal purple in gear boxes because of the heat and relatively low cost as they take so little. Can't point you to any science as for why it's good to do it just makes me feel warm and fuzzy..
RTV for a gasket is good to if you apply it correctly. Here's what I do - Clean both sufaces, run a bead about 1/8" in diameter, let it set-up for 10 or 15 minutes, place the cover on and start the bolts but leave them loose! let the RTV set-up for at least another hour or so (or over night if your not in a hurry). Tighten the bolts and your done.
The two biggest problems many people have using RTV:
1 - not cleaning the mating surfaces.
2 - squeezing all of the sealant out by wrenching the cover in place while it is still wet.
Also, be careful with rags, not a huge deal with a gear box but when cleaning rough cast surfaces they can leave as much lint behind as junk they take out. If you ever want to see how much lint regular rags leave behind, rebuild an automatic transmission with them. If your lucky it'll go 100 miles more likely about 4 blocks:ashamed:
