MacBook Pro :: Why Did Heat Up While On Standby

Today at school, I was using my laptop as normal. During lunch time I just closed the laptop display screen (so it goes on standby) and placed it in my bag. 1 hour and a half later, I go into my bag to reach for my book. My whole bag and books were VERY warm. I touched my laptop case to find that it was even warmer. I pulled out my laptop and I had to set it down immediately because it was far too hot to touch; eggs could have been fried on it (no exagerration). I was scared to open it, so I placed it outside in the cool air and now it has cooled down and I've started up again. This has never happened before, I've never dropped it and my laptop is just a year old this month (convenient now, that the guarantee just expired ).Problems first started occuring when I updated to Lion. First thing I noticed, is that it starts up and shuts down SO slowly (slower than a PC, believe it or not) and I only have 53,15 GB out of the 319,21 GB available used. So there is 266 GB FREE space. So I figured this cannot be the memory.  After 2 months or so, I also noticed that when I turn on my computer, the Apple sign on the startup comes out very stretched, sometimes it comes up on the left hand corner and the rest of the screen isn't white but coloured lines. 3 days ago, I noticed the fan was making a funny sound. This stopped 2 days later, then today randomly on standby it beyond heated up. Why is this happening? MUST I go to the shop? (I'm a student and cannot afford 500EUR repairs at the moment, other than the fact I cannot live without my laptop for 6-8 weeks as I have all my coursework to do, etc.)

Info:
MacBook Pro (15-inch Mid 2010), Mac OS X (10.7.3)