Having been involved with old British sports cars for several decades, I can attest that welding is a valuable skill.
Get ahold of Franklin Barbecue by Aaron Franklin and Jordan MacKay. Not a true cookbook, it takes you through the process of good Central Texas barbecue. Each chapter covers a different aspect of barbecue, like smoker construction (or remodeling a store-bought model), the wood, fires, meat selection and the cook, etc. It's a great read. I've used it to improve my weekly barbecue at the camp.
Depends if you want a certification or just a course for amateurs. I can do very basic stick welding, learned that at university, the course I booked for this summer is an amateur-grade MIG/MAG welding weekend session that runs for about 300€. Professional courses... well, way, way more. I just love to be able to do it myself at a basic level.
I'll always have a special place in my heart for offsets. The first two smokers I learned on were side by sides...and I still love'em! But at home I use a BackWoods Fatboy smoker. If I had to replace it...I'd do so with another FatBoy or something very similar. The thing really holds the temp...and you can smoke in temperatures well below freezing.
When looking at smokers keep in mind that all verticals are not the same, just as all offsets are not the same and all water smokers are not the same. Look at the construction and think about retaining heat, flow of air and size needed.