Venture Head Gasket? K-SEAL?

Hi, I just bought a 2000 Chevy Venture LS with 170,000 miles. Did some work about $500.00 worth and got it inspected. I replaced the following. 2 Tie Rod Ends, 2 New tires, New headlights and side markers, front rotors and brake pads and flushed the coolant system and also just the heater core. Had some black chunks come out. Flushed with water both ways and put air both ways then flushed water both ways again. Wanted to make sure I got most of anything out. YES I have bleed the 2 screws 3 days or so in a row and added antifreeze after I did bleed them. First mini van we have owned and I love it!! Well I "THINK" I know why she sold it for $450.00. Which I don't think is that bad. Only been driving it for about a week and every other day or so I have had to add antifreeze. When the temp gauge goes up I lose heat. When it drops I have heat back. What I have read in the internet these vans are known for head gaskets. JUST wondering if I should try K-SEAL first?
I have a 1996 Pontiac Grand Am. With the Quad 4 in it. Which couple times blew white smoke out the exhaust. And I was adding antifreeze about once a month. I added K-SEAL and ever since I did it I haven't added any more antifreeze or had white smoke come out. It's been about 6 months since I added it.
Should I try to add K-SEAL? If so and it doesn't work will it be a pain in the as* when I change the head gasket with that stuff in the system? I'm very mechanically incline. I WILL buy Fel Pro Gaskets. I know the gasket kit is around $200.00. Any one have an idea what else I should buy and total how much besides the head gasket kit? Like new head bolts? I don't mind putting another $500.00 in to it since have little under $1000.00 in to it now. The vans in great shape. I'll try to post a pic.
Thanks, Dan
p.s. I would buy a dealers service manual. Not an after market one.

You are creating an air pocket, because you have a leak.....have you checked for EXTERNAL leaks?

I put the K-SEAL in it yesterday. Went 6 or 7 miles my temp gauge went up above half way and the only time it goes up there is when it goes to the red mark. When it half way it dropped down and hasn't gone beyond the mark above the quarter. The temp gauge only moves between 2 or 3 lines now. Before it was bouncing everywhere. I drove it around about an hour yesterday. I have all heat now. I added some antifreeze this morning before I started it to top it off. It's from losing it before the K-SEAL started to work I think. To and from work today the light never came on and it didn't go past the mark above the quarter. I REALLY hope this works on this van like it did on my Pontiac. I have not looked for any leaks. I live in Maine and right now it's freezing outside. lol I'll keep you posted to see if the K-SEAL is still working.
Thanks, Dan

That type of stuff might plug something up. Like radiator, heater core, etc....

If you do gaskets, replace head bolts, and intake gaskets (get the better intake gaskets - they might be the culprit).....