Sleeping depends very much on wether you want to sleep outside or not. Most people don't sleep in tents in the Alps, they sleep in huts. All the gear that's required for that is a silk or cotton bag liner and clothes to wear to sleep. You will usually get warm food and drink in them too. It is helicoptered in to the higher more remote ones, so prices can be a bit steep.
As for weather: You will cross the Hauptkamm (not sure what the english word is, basically the highest mountain ranges in the area). They sit right at the Austrian border to Italy and are high. I'm not sure which way you are planing to go but my guess would be the E5? If you do, it crosses the Hauptkamm at about 3.000 metres and a couple glaciers are gonna be right next to you.
In summer it can drop to around 0 C fast (3 hours maybe, maybe even less), together with rain and/or snow. Or it might just rain for a couple days or actually be very nice and warm. The Hauptkamm is also where the weather in Europe gets divided between north and south. The north side is usually a lot wetter and colder then the south side (going so far as heavy rain and cold and windy on the north side and sun and 10 degrees more on the south side – about 200 metres through a tunnel). The weather on the south side is also more stable then on the north side. A lot of the higher peaks do have micro climates (although this is more pronounced in Switzerland and France because the mountains are higher there). The locals, especially in the huts usually know what to expect, the weather forecast on the radio does not.
The infrastructure is generally excellent. Your mobile phone will almost always work and on routes like the E5 you won't really be alone in summer (the huts manage to provide a sleeping place for everyone though). If you want to look at a hut have a look here: http://www.braunschweiger-huette.at/ (this one is at 2.759 metres).
Keep in mind that you won't be able to plan your days based on mileage. Because the mountain ranges run from east to west, you are forced to descend into the valleys and get up to a pass all the time. Height differences between of about 700 – 1,000 metres between valley and pass are common.
As for clothing: Rain jacket (eVent or Gore) – no ponchos, almost all trails have exposed sections where a poncho turns you into a sail and makes gripping rock harder. Rain pants, shirt, thin fleece jumper and either a thick fleece or a puffy jacket. You should be warm and protected enough to sit out at least a night foul weather – although help usually arrives faster then that, especially if you call a large hut for help. Oh, you will spend at least half your time way above the tree line.
Trail runners are usually not recommended, but weather they work for you or not depends a lot on how you can deal with long stretches over rock, scree fields and loose rocky soil. If you use trail runners I would recommend some lightweight gaiters.
If you want to use a tent/bivy: You can almost certainly forget stealth camping in the tourist regions or large trails – the valleys are densely populated and the hills are full of people. Almost every inch in the mountains is used as pasture. If it isn't you can expect a surface made of rocks and ice.
In general though I would not recommend even carrying anything like that – except for an emergency bivy bag – and just use the huts. You can't go much lighter then that and most trails aren't designed to be walked with a lot of gear and are often exposed. That said: You can use it and I have spend some very nice nights up there.
Guides exist at least for the E5. Otherwise you can find good maps and plan your trip using them (keep altitude changes in mind though). Except for Meran itself just about every local will speak German – other languages depend on education and wether or not you're in Italy or Austria. In Meran itself almost everyone will speak Italian.
