Firstly well done on getting a Triumph, you won't regret it ....... honest
Ok, where to start:
noisy exhaust, a Herald is not that noisy but will be louder than a modern euro-box and don't forget you've not got a steel and glass roof to insulate
you from the outside world.
If by fixed you mean welded, then these never last. A complete system isn't dear and if funds allow go for stainless.
Clutch/pulling away problems probaby down to dodgy clutch hydraulics (easily and cheaply sorted) or possibly down to a sticking clutch release bearing.
This needs the gearbox out but don't panic, I had a similar problem in the same model when I was 18 and could get the box in and out by myself in about
1 1/2 hours. Not difficult just a bit fiddly. The judder when pulling away could be from a contaminated clutch plate.
Smoke from the exhaust can be steam. Are you certain what it is? Either way, shouldn't be there and if I were you, I would check the oil and water for
contamination (blowing head gasket). If still has a full radiator then the engine is a bit tired. Does it smoke when pulling away after being
stationary in traffic for a while and also on over-run? If so valve guides worn, if it does it under load then the piston rings are on their way out.
Either way engine will need some work.
To be honest, your best bet is to get yourself and your Herald along to your nearest area meeting and do some serious chatting and car park
diagnostics. You might even find someone with a surplus engine or at the very least will be certain to get some offers of help.
Still it can't be too bad, that was a long run home wasn't it?
Best of luck
Clive