Small Engines (Lawn Mowers, etc.): possible blown gasket?, small engine mechanic, gmc sonoma

Question
I have 5 year old Sears riding mower with a B&S 31C707 engine. We had to replace the cam about 2 years ago. Went to crank it today and could not get it to start. Noticed a lot of oil/grime in the front around the exhaust area. Pulled, cleaned, and re-installed the plug and it started; however, it began smoking really bad. Happened to a GMC Sonoma I once had and that turned out to be a blown headgasket. Is it possible I have the same problem with this B&S? I am not a small engine mechanic by any stretch of the imagination, but can figure out most things with enough instruction. If you think it is most likely that the engine needs an overhaul, can you recommend a book illustrating what needs to be done and what parts to purchase? Would I require any specialty tools (i.e. timing light)? Would you recommend I not attempt the repair and seek a qualified technician in my area? I understand how a gas engine works and its basic parts, but have never tried to rebuild one.  Thanks!

Answer
Ok slow down there Hunter. Let's not go putting the cart before the horsey. First things first, a good tech never does needless work, at the expense of wasting a customers time. or money. The very first thing you need to do is a compression test. A cylinder leak down test would be good too, but doubt you have a leak down tester. Smoke can be a symptom of a variety of  things. Just what color is the smoke? Have you been using oil. How full is the oil now? Has it sat for some period of time that oil pooled on top of the piston after sitting for a long period this happens. Also once started you never mentioned how did it run? Did the oil smoking stop, or lessen? ....lets start here, and then go forward..........Tom