blown head gasket BA V6 '94 Astina

[Frostex]

So the story begins 2 weeks ago, when i was driving along and i noticed my temps were REALLY hot (basically max temp on the gauge). so i pull over, let it cool down and topped up the coolant tank. took all of my 2L bottle from the boot and another ~3-4L when i got home.

no problems for a week, then exact same situation happend again (but not as hot cause i had been paying extra attention to temps). So i ring the mechanic on friday he says to bring it in thursday.
On tuesday it happend again but i was at home when i noticed the temp (think it was running hot for 2-3 mins) so left it in driveway over night to fill in the morning. In the morning it had a lot of difficulty turning over but did after about 1-2 mins of on/off trying + pushing gas.

No problems since then (driven about 100kms in the meantime) but i just got it back from the mechanic and he said it was a blown head gasket and it would cost $3500 to fix.
He said that something had been slowly deteriorating and it was inevitable but when it wouldn't turn over that was when it got really ****ed.

So my questions are:
1. Is $3500 an accurate quote?
2. What do i risk if i get in the car and drive in its current condition?
3. Are there any other options?
4. I have a few rather tech savvy friends who i havnt spoken to yet but would be willing to help. Assuming we could do all labour and stuff ourselves (im a noob, but they are quite experienced), what costs am i looking at then?
5. if scenario 4 is realistic, can anybody give me some information on what is involved (preferably more specific than completely disassembling the engine)
6. car was purchased about 5 years ago with 100,000kms for ~$9000 in immaculate condition, if i was to sell it in its current condition, what return would i be looking at?